I ph @6.8 for soil . I was running 6.2 to 6.5 . I would get yellowing like this at 6.2 to 6.5 I accidently started ph @6.8 this grow and I have 2 to 3 weeks left and she is just now started to fade a little. I know with my nutrients TPS Component series that all my nutes are avalible at 6.8 and not as much at 6.2. I also kept my temps cooler this run. The auto sees 77 f but has gone up to 80f (not long) rh in the begining was 60% and I am running 48% to 43% rh late flower. My photo gets to 82 f tops and down to 78f nights. I am in late veg @55% rh.

I am laying these out there trying to figure what went wrong in my past grows . So far I am guessing heat and ph too low . These are the two things I have changed and I am having better luck this time. 

My past grow temps were 85f day and 81f night rh 70% seedling and 60%flowering. 

I would love to hear your total specs and compare. I am not telling you this is the problem I am just trying to see what differences we have . Maybe there is something there maybe not.

Thanks bud