In 4th week of flower. Plants look great and seem to be happy. A few plants are starting to yellow at top in spots. I'm sure it a deficientey of some sort and I can't seem to narrow it down
Its hard to tell in that light. Calcium deficiency would be top part of plant but would have brownish small spots that are easy for you to see up close.
Magnesium deficiency would be lower down on older leaves.
Does this picture look similar (your lights are on so hard for me to tell)
I was having temp issues when I turned the ballast up to 75% on 1000 watt ballast and I also wasn't watering everyday like I should've been. I'm using cyco nutes and I added Cali Magic to the feed schedule