What’s wrong?

I water these plants every 2 days since they drink all of the water and the pots are light. The 220w light is on max since these clones are supposed to be in full veg (they were fine on max a couple weeks ago) which is at 650ish lumens read by my soil tester tool that also reads brightness. The water is ultrapure since I have an RO system with a water softener. pH at 6.5 even though the alkalinity is only 3.

I wonder if using normal tap water will fix this. What are your thoughts?