Just can't get it right

Dwc 8gl res, gh flora nutes, cal/mag 5ml/gl,600w, ph 6.3 when I fill, drops to 5.2 in a few days when I top it off, two fans, one big one blowing the scrog canopy, smaller one blowing the lollipopped bottom, 84° 35-45% rh lights on, 75° 50-55% rh lights off. If you need anything else please let me know. Thank you so much guys. week 5 of 12/12, week 3 of actual flower.

Help a brother out lol

I'm no pro but the fading looks like mag def to me. Brown tips/edges indicate nute burn so maybe you have a lock out. I would do a rez change, water only to ph 6.0, wait 24 hours before adding nutes back at PPM of 600. Could also add some frozen liter bottles to rez to get temps down too. Good luck!