PH 6.5 is only for soil. Soilless mix needs a slightly lower PH in the range of 5.8 and 6.0Looks like its in need of calcium give it calmag thats why leaves are going yellow and 5.8 ph too low go to 6.5
Light stress was also my first thought. The lower leaves have discoloration from it as well. Those are more sploched and bleached looking. I've seen the same on some of my plants.The inter veinal discoloration could be a few things. My first thought would be it’s light related. If not, I’d look at N & Mg
Probably Mg (definitely not Ca, no rust spots) and it needs 6.0 for good uptake. Also have you been spraying them with something, hopefully that isn't PM.