Bottom leaves drooping/falling Hydro flower

Hi guys , this is my first try at hydro. Problem started after switching to flower & refilling my big tote . I tried lowering water level but it doesn’t seem to help . Any idea ? Thanks
PPM 1300
PH 5.8
Plant was fine at 1300+ in veg with no sign of burn

Cold water will droop a plant,when switching to bloom nutes i mix 50/50 veg,bloom keeps the N up.

Lowering water level is never a good idea,roots live in aerated water, take that away and they'll droop.

Water temp is at 22 \ 23 cielsus atm . Been a week since the water change . Not sure what could cause that . I will try racalibrating my ph pen.

When I changed my water I let the water go lower then normal for easier transport(it's heavy as **) I though maybe the roots crated oxygen root then I drowned it or something .