My ph since I’ve been in flower rarely raises usually goes downOk so it's not the light.... my ph after mixing nutrient solution is usually 5.5. Then it'll rise to 6.1 and as the water level continues to lower, the ph drops. Usually to 5.5 again.. I add back plain water and that raises my ph to 5.7. I let it do that twice(about 2 1/2 days) then I do a res change.