Top leaves turning yellow and crunchy

[Mike_3]

Day 28 of flower why are my top leaves only turning yellow and crunchy turning inwards? I’m not feeding very high ppms only about 700 6.5 ph. I’m in pro mix only feeding 6.5 ph at the moment because my ph has been coming out 5.8 when I take run out. I’ve tried flushing them early flower didn’t seem to help with fixing ph issue. Please help I also highly doubt this is from light stress.

 

[SofaKingHigh]

Day 28 of flower why are my top leaves only turning yellow and crunchy turning inwards? I’m not feeding very high ppms only about 700 6.5 ph. I’m in pro mix only feeding 6.5 ph at the moment because my ph has been coming out 5.8 when I take run out. I’ve tried flushing them early flower didn’t seem to help with fixing ph issue. Please help I also highly doubt this is from light stress.

How far away is your lights? Also what’s your humidity

 

[HaveApuff]

How often are you feeding them 700 ppm?