Looks like a cal def but not sure how because i put 8tbsp of lime so i assume its too much or its locking out again. Hmm i didnt notice. Looks to be mainly in the middle. Some in the lower and few higher up but tops look great.
I've been thinking about what this might be.
Eliminate or address this list.
pH fluctuations
Uneven moisture levels in growing media
High Humidity
Fan blowing constantly on plants
To high N P K
Common nutrients issues (with a good nutrients line)
Calsium
Magnesium
Nitrogen
Can lead to not so common issues
Iron
Boron
Calcium shows in new developed leaves-middle growth
Magnesium shows in older growth on leaves exposed to light
They are mobile elements
Hard to overdose on them but have seen lock out in peat moss with excess use.
Too much "P" can show as mag def also.
Boron is rare but, is a factor. Usually alongside other symptoms.
Anything else? Would be distinctive.
Stunted growth, yellowing, wilted leaves?
I think your fan is to close, to hard, evaporation faster than replenished causes leaf spotting on the side of the fan. You rotate the pots causing it to appear all over the plant!
ISSUE SOLVED!!!
TURN THE FAN DOWN!
LOL
Seriously I hope you figure it out.