Light stress?

[Roach]

Problem: Yellow curling tips on new growth

Medium/grow method: Biobizz Light Mix

Feed: and supplements used: 1ml and up to 2 ml per litre of calmag & root juice respectively.

water source: RO been mixing in roughly 1 part in 12 of hot filtered tap to help temperature and stabilising PH

Strain/age: FB Purple Lemonade, Smoothie, Gelato.

light used: 2x 55w autocob's + Grownorthern ms0006

Climate: temp 70-77, RH 50-60

Additional info: 7x4x2 tent HxWxD

Pics are of the Purp Lemo (top) and Smoothie. The Gelato is nowhere near as bad and is the shortest which figures if I'm right. With hindsight I probably should have turned the Blurple up in stages instead of full whack on day 7 or whatever it was. I've backed them off as far as possible (33' blurp/30' cobs) and (reluctantly lol) turned the panel down to 2 thirds.
2 questions I guess. First am i right is it light stress ? Second do you reckon I'll be able to ramp up the panel when they're flowering?
I think the cobs are driven at full whack? (sorry another question) and the panel at about 186w making 296w in a 4x2 which I believe is 37w per sq ft.
Cheers in advance for any help good people!

 

[Olderfart]

FWIW, I found that many total watts were too much in my 2x4. 37 watts/sq ft. may be excessive with any decent LED's, much less the highly effective autocobs. Given others' results with the autocobs, I would think the blurple is excess, but I will be interested to see what more experienced growers here have to say.

 

[automan2]

I'm running pretty much the same setup... same lights, same medium, same strains. My wattage is 275 in 6 sq ft.so around 45w sq ft. Sometimes I add a blurple (100w) as a fill-in light for finishing....never had any light stress because of too much light. Those tip curls don't look like anything light related.
I'd suggest double checking ph... I only water with DI to eliminate ph issues for a month, then ph our well water to 6.4 or close.

 

[Sleeper143]

I use same soil, and biobizz nutes. Not sure how old those ladies are but looks like nute burn on the tips. What are you feeding apart from the root juice and calmag? I’m on day 13 of my current grow and I won’t be adding calmag until some point maybe in week 3 - and then at 0.5ml per litre (gradually increasing over the grow to a max of 2ml pl). Light mix will have enough nutrients in it to last 3 weeks no problem. Also, I see you use RO water and add some tap water to warm it up. What is your tap water like (hard/soft) as that will be supplying some ca and mg too (mind you at 1:12 pretty sure the levels will be so low they won’t cause issues). I really think you’re over doing the calmag at the moment if she is less than 5weeks old - I think I went up to 2ml pl in week 6 of my last grow.

 

[Roach]

Cheers Gents interesting stuff! I've not watered to run off yet so I'll do that next time and see what that's saying. My initial pot soak was at PH 5.9 as I had no way of adjusting at the time. Since then I've watered at 6.3, 6.5, 6.8 and then last night at 6.9 figuring if I didn't need to adjust I won't but do have the biobizz ph+ and down which I used on the second and third watering.
Re the calmag I've a feeling your onto something there. I even used it in the initial pot soak. The idea being to help stabilise the PH of the RO and was worried about lack of minerals as I used no tap whatsoever for that. Thinking about it there's probably enough cal & mag within the medium to sustain such tiny plants when I've added the tap it takes my ppm from about 4 - 85 so again probably enough in there for early growth at least.
Moving forward I'll get a runoff PH reading and leave the calmag out for the next two or three watering at least and see how they go!

 

[Roach]

Sorry meant to add they're on day 24 I gave 2 of them 0.25 grow per litre for the first time last night. The purp lemo had had two feeds like that as I thought she was looking a bit k deficient.

 

[Roach]

@Sleeper143 do you think dropping the cal mag will be enough or would you recommend a flush?

 

[automan2]

It's kinda the last resort, but flushing is usually used only for over nute issues which won't hurt nearly as bad as not flushing if that's the case. I rarely flush bio bizz light mix and then only if I tried to push too many nutes. With 7-8 flowering plants at one time perpetually, I do f'up ….. but shit, I'm old and stoned.
Never heard of precharging light mix....may have started the problem at the gitgo. RO and DI are both devoid of minerals but I've never heard of it being an issue used by itself. I've used DI for years for the first 3 weeks on all my plants. Your first ph of 5.9 added to eventual probs too I would imagine. With the short life span, autos don't have much time to recover so i'd never flush in flower.

 

[Capt.Quirk]

I saw a picture of these symptoms at GWE's plant problem section and it was indeed light stress. Good that you caught it early, as it can
become worse. Much worse.

 

[Roach]

It's kinda the last resort, but flushing is usually used only for over nute issues which won't hurt nearly as bad as not flushing if that's the case. I rarely flush bio bizz light mix and then only if I tried to push too many nutes. With 7-8 flowering plants at one time perpetually, I do f'up ….. but shit, I'm old and stoned.
Never heard of precharging light mix....may have started the problem at the gitgo. RO and DI are both devoid of minerals but I've never heard of it being an issue used by itself. I've used DI for years for the first 3 weeks on all my plants. Your first ph of 5.9 added to eventual probs too I would imagine. With the short life span, autos don't have much time to recover so i'd never flush in flower.

Thanks man I'll stick to the original plan and water to run off with some plain ph rather than flush then and omit cal mag from my next couple of feeds and keep an eye on em.