My friend is having this problem with his leaves turning stiff and yellow and burning up. Buds look great and healthy. Plants have recently been flushed with Clearex and new solution made to an EC at 1.77

One thing is the damn PH keeps rising. He is using citric acid because he gets it free and it's supposed to be good to use. But these damn leaves are just wanting to burn up like trees in the fall.

This is a DWC system with a lot of circulation. Roots are a little yellow but no major rott. Harvest should be ready soon. I just don't get what's burning the leaves up. Maybe he should try lowering EC to around 1,5?