What’s going on

Setup 4x4 GG TENT
HLG550 v2 rspec
Fox farm ocean forest
Why are upper leaves turning this color .
This is my first grow and everything seemed to be going decent. Any help will be appreciated

This used to happen to me all the time in flower when I grew in potting soil. I never tried to diagnose it. But looking at my garden saver book, it looks most like an iron deficiency. Idk if that's correct, but it was common for me in mid to late flower. I bet its nutrient lockout from salt build up. Since it's hard to flush in soil. This is just a guess

My guess is a calcium def possibly from not enough left in your soil or possibly ph related. Renfro recommends a ph of 6.5-6.8 I believe for dtw soiless. Problems seem to arise often for me as well during early flower.

Looks like your leaves are getting their fall colours to me. My Hindu Kush goes almost black by the time it's done.