'Rust' Spots on Two Leaves

[OttoCBD]

-Problem: Two leaves have brownish rust spots on them. They're definitely not from nutes splashing on them since they're nowhere near where I top the res off. I had noticed this a few days ago and I've been keeping an eye on it. So far as I can tell, it doesn't seem to be getting worse and is only on the two leaves as indicated below.

-Medium/grow method: Drip/DWC Waterfarm

-Feed and supplements used: Advanced Nutrients Sensi Bloom A and B at 15ml each per 2 gallons (A 3-0-0 and B 2-4-8), Sensizyme at 16ml per 2 gallons, Tarantula at 15ml per 2 gallons, Carboload at 15ml per 2 gallons and Sensi Cal-Mag Xtra at 7ml per 2 gallons. When need be, I'm topping off with 3ml each of A and B and 3ml of Carboload (per gallon)

-Water source: Tap with a pH of 7. Never checked EC, ppm or pH of the res

-Strain and age: Fast Buds CBD Crack / 8th week

-Climate: Temps have been no higher than 78 and no lower than 60 and RH is at 45

- Light used: Mars Hydro TS600 (100w at the wall in a 2'x2' space) , two 42w 2500k CFLs, and one 30w 2 foot blurple all on an 18/6 schedule and about 16 inches above the canopy.

-Additional info: During the prior week's res change, I had cut back on the Cal-Mag from 7ml/2 gallons to 3ml/2 gallons in an attempt to cut back on excess N during flowering. Thinking that it was lacking from the Cal-Mag, I injected 6ml directly into the res. Normally, when I mix nutes, I always add the Cal-Mag first and let it sit for a few minutes before I add the base nutes etc. So, this may be where it stems from. I've also read that this can happen due to too much wind or the lights being too close. Anyway, here's what they look like.

 

[OttoCBD]

I think what I'm going to do is start giving it 12ml per 2 gallons which is a compromise between what TaNg suggests (4ml per gal) and what AN suggests (8ml per gallon).

 

[Wattzzup]

Cal/mag deficiency IMO

possible lockout causing it if you’re adding it.

 

[OttoCBD]

Cal/mag deficiency IMO

possible lockout causing it if you’re adding it.

Thanks, @Wattzzup. I figured that deficiency might be the case. I think the issue is that I haven't been adding enough. I started out giving it 7.5 ml per 2 gallons and slowly cut it back over the past few weeks. Despite what I said in the previous post, I'll be bring it back up to 7.5 when I change the res tomorrow.

 

[Wattzzup]

Thanks, @Wattzzup. I figured that deficiency might be the case. I think the issue is that I haven't been adding enough. I started out giving it 7.5 ml per 2 gallons and slowly cut it back over the past few weeks. Despite what I said in the previous post, I'll be bring it back up to 7.5 when I change the res tomorrow.

Unfortunately I’m not familiar with drip/dwc so I can’t help with that part

 

[OttoCBD]

I think I have a handle on it. I did a res change and I'll keep an eye on it for the next few days. In the event that what I was dealing with may have been a calcium deficiency (the rust spots seem to be a symptom for both Ca and Mg) ..will that contribute a great deal to the possibility of a 'diminished harvest' and slow flower development as indicated in the pic below? Being new to autos, I'm not sure if the development / size of the buds in the previously posted photos is normal for a plant at day 51.

 

[Waira]

- Otto, never be complacent about res' pH!... "pH perfect" or not, with all the other influencing factors acting on the res' solution, it can drift out of range, and in hydro, it's a very narrow one!
The symptoms could be P defc. or Ca, both can present similarly or at the same time,... If it's limited to just a couple places, not spreading, the I suspect you had a pH hiccup affecting availability temporarily.... do yourself a solid, get a pH and TDS meter and monitor both these daily, both inputs and the res',... without them , you are flying blind!

 

[OttoCBD]

- Otto, never be complacent about res' pH!... "pH perfect" or not, with all the other influencing factors acting on the res' solution, it can drift out of range, and in hydro, it's a very narrow one!
The symptoms could be P defc. or Ca, both can present similarly or at the same time,... If it's limited to just a couple places, not spreading, the I suspect you had a pH hiccup affecting availability temporarily.... do yourself a solid, get a pH and TDS meter and monitor both these daily, both inputs and the res',... without them , you are flying blind!

View attachment 1169848

Thanks for the info and suggestion but I'll keep on keeping it simple.