Spots on one of four seedlings + slow growth, Genetic or disease?

[jER]

Hello Everyone!
This is my first post here, and my first attempt at growing autoflowers. On Dec 1st I germinated 4 seeds, Jack Herer Auto Fem from Crop King Seeds. I plan to grow them in a RWDC setup in a 3' x 3' tent. I started them in 1" rockwool cubes and they sprouted quickly, shooting up 1" above the rockwool overnight. The Cotyledons opened up (one had a seed coat stuck but I managed to help it free) and small buds of true leaves were showing. All four seedlings basically stalled and barely grew at all for the first week. I had been watering with bottled water (Aquafina) that I had Ph'd to 5.5-6. I switched to tap water (carbon filtered and PH'd) after the first week and the seedlings started to grow a little better, maybe they needed a bit more minerals than the bottled water had but It could have been a couple things I will explain later. Anyway, I am now on day 14 and my seedlings are still working on the second true leaves. From many of the journals I have read on here it seems my seedlings are pretty far behind schedule.
One of the four seedlings has strange spots on it's leaves. It has had these since the leaves formed and it looks like the 2nd set of leaves are showing the same thing. None of the other 3 seem to have these spots.I am not sure if this is mildew or a genetic thing or deficiency. I am wondering if I should cull it to keep the others from getting sick (or cull all four due to slow growth/stunting and start over). I haven't fed them any nutrients yet, just water. If anyone has time to take a look at the attached pics and let me know what you think, I would very much appreciate it!

 

[jER]

I guess I am supposed to fill out the infirmary form, my bad, didn't notice it at first, here goes:
Problem: Spots on seedling leaves (only 1 seedling out of 4), Very slow growth on all 4 seedlings. Currently Day 14 since germ.

Medium/grow method: 1" Rockwool cubes (to be planted in hydrotron for RDWC)

Feed: and supplements used: none as of yet

water source: Origionally used bottled water, switched to carbon filtered tap water (ph'd down to 5-6)

Strain/age: Jack Herer Auto Feminized from Crop King Seeds

light used: Mars II pro 600W, currently 28" away on veg mode

Climate: 3'x3' tent, temps 20-26C, Humidity 30-40% (Its very dry here in Alberta, I`ve got the DWC system circulating to try to increase the humidity)

Additional info:
possible reasons for slow growth?:
1. I started the cubes by soaking them briefly in Ph'd bottled water (Aquafina) as the CKS germ instructions said to only use RO water for Germ. I think since the aquafina is de-mineralized and I am sprouting in rockwool that there aren't enough trace minerals to sustain early growth?
2. I Ph'd the bottled water and accidently overshot with PH Down, I then added PH Up to compensate which I have since read is a no no... oops. I talked to CKS and they said to never adjust the PH of water for seedlings at all? (Sounds wrong to me)
3. I originally had the cubes in a small dome to increase humidity, I also had them on a small heating mat on low (cubes @ 25-29C) when I germinated them. I noticed a lot of condesation on the top of the dome and the cubes started to smell a little sour. I removed the dome and a paper towel the cubes were sitting on and the smell went away. The seedlings didn't damp off and look healthy but growth is still very slow. I watered them with a quick dunk to the bottom 1/4 of the cube with fresh filtered tap water and a tiny bit of voodoo juice (0.25ml/L). They started growing better after this.

 

[Mr Green Fingers]

I would put them in there final pots so the roots can grow as they won't be able to develop where you have them now, you should've put them in there final pots when the seeds popped and your roots would be in res by now!

 

[jER]

Thanks for the reply, i am planning on puting them in the netpots asap, unless the spotted one is indeed sick and i need to cull it or treat it and do a clean down of the tent first.

 

[Mr Green Fingers]

Autos only have a short lifespan, personally if I was you I would pop another seed and put straight into final pot as by 14 days it should be a lot more developed then yours is but I've only done a few grows in DWC so no expert so maybe wait for some more advice

 

[jER]

Yeah these seeds are growing super slowly, I am not sure what I am doing wrong and I want to figure it out before making the same mistakes on a new Set of expensive seeds. I bought my rdwc setup as a kit from some local guys and the way they have it setup the water level is 4-5 inches below the bottom if the net pot. It pumps water into the bottom of the 4 buckets through some 1/2" pvc and then overflows back to the control rez through a 3/4" pvc. It seems to cycle well and the water level stays stable in all 4 buckets, but the level itself is pretty low. I am going to have to hand water for a while till the roots get long enough to hit the water. I will probably run these runts out a while so I can make the rest of the mistakes I know i will make while learning to run this dwc.

 

[jER]

So my plants are starting to grow a bit faster, I have them in the buckets and roots are starting to show out the net pots. Things are looking better except for one plant where all the new growth has come in bright yellow (3rd set of leaves). I am not sure why, all 4 are getting the same water and the same lights but only one has this yellow growth. Despite being yellow the leaves are still growing and that seedling has some of the longest roots out of the 4. I thought it must be a lockout issue, pH was around 6 so i brought it down to 5.5 and flushed some clean pH'd water through the cube and hydrotron. The rez currently has some light nutrients in it (0.5ml/L of AN mirco/grow/bloom) but none of the roots are quite hitting the water yet. The bubbles to keep the bottom of the hydrotron fairly saturated and the cubes are staying moist with a little handwatering once a day. Any idea what is causing the yellow growth? These are now 21 days since they germed.

 

[Mr Green Fingers]

Glad you got them in there final pots! Can you give us more info, light distances etc and also post some pics in natural light as hard to see what's going on under the blurple light.
Maybe this AN nutrient calculator will help you, I would start at 1/4 strength of what it says but it will give you the right ratios of what you need to use at least!
https://www.advancednutrients.com/nutrient-calculator/

 

[jER]

Yes I certainly can,
The yellow growth is starting to get some green back in it, still not sure what happened, guessing it was stress from potting it in the hydrotron? Some of the other plants are showing some verigation in the leaves now like the spotted one, might just be the genetics? The spotted one looks to be a bit of a mutant having some 2 blade leaves etc.
I have the light about 2' from the tops right now. I was running just the veg light setting but have now switched on both veg and bloom spectrums.
I have seen that AN calculator and my rez is currently at 1/4 strength.

 

[Mr Green Fingers]

Yes I certainly can,
The yellow growth is starting to get some green back in it, still not sure what happened, guessing it was stress from potting it in the hydrotron? Some of the other plants are showing some verigation in the leaves now like the spotted one, might just be the genetics? The spotted one looks to be a bit of a mutant having some 2 blade leaves etc.
I have the light about 2' from the tops right now. I was running just the veg light setting but have now switched on both veg and bloom spectrums.
I have seen that AN calculator and my rez is currently at 1/4 strength. View attachment 990548 View attachment 990549 View attachment 990550 View attachment 990551

I wouldn't worry to much at this stage, personally I would move the light up a bit, start using calmag if your not already and just look for how the new growth looks, I think the one with the yellow leaves just needs a feed but you are now so all good, regarding the variegated leaves, this often happens to the first few sets but they normally grow out of it!