light green leaves with brown spots

You’re correct - this is an early stage calmag deficiency and it’s common that it will represent on the larger fan leaves first. Every strain will have slightly different needs so it’s not unusual to see it happen to 1 plant and not another. Easily resolved with a calmag supplement. I personally use calmag + from botanicare but GH has a Cali-magic as well. These are the 2 most common and u should always have a supply on hand every grow. Start with 1ml/L and that should clear this up within a couple weeks. Continue with it until you’re in the last 2-3 weeks of flower at which point it won’t be needed any longer. Helpful hint - odds are good you still won’t run into issues by adding calmag to current nute regimen for all plants - even if not really needed. This might be more convenient for you but I honestly haven’t taken a full look at your diary. Good luck with it👍

Calcium deficiency is likely. If only 3 leaves are showing problems though, I would only increase calcium slightly. Also if you have too much P or K, calcium and micronutrients can get locked out so adding calcium won't help your deficiency in that case. Hopefully this helps!

Gonna agree with you a cal mag supplement may be needed. Should take pictures in white light easier to read all signs of problems. I would check run off ph first. Should get about 20 percent run off each watering. Check the beginning of run off and end. Tells you where you were and where you stopped. Plus removes uses up salts from old chemicals that can cause ph problems as well. If ph is in check then adding cal mag would solve it. Regardless it's a good supplemental to have and use. Good luck and happy growing 🌲🌲🌲👊

I've also seen this could be overwatering problem but I'm confused it only shows on a few leaves.. plant is 5 weeks old RQS Easy Bud Automatic, in flowering.. other 3 plants don't show any signs of this.. I feed them all the same only I watered this one a bit more because she is much bigger then other 3, and week older.. thanks for all info and tips