Dirtydogs446 , Looks similar to an issue I recently had. The soil was colder than it should've been. The canopy was warm and the humidity was low like yours. It caused what at first looked like a situation of having an excess of nitrogen then later it appeared to be a magnesium and phosphorus issue. The canopy temp was in low to mid seventies (basement was full of drafts). But the soil was much colder. Lifted them off of the floor, raised the light and put a heater near by. I also fixed the drafts. Now the problem has sorted itself out. Made it look like phosphorus and magnesium deficiency but pretty sure it was mostly temperature related. Warm canopy cold soil, causes issues. You could add some magnesium maybe and maybe try watering a little less.
You already have roots coming out of your 5 gallon buckets? Didn't you just transplant like ten days ago? That's pretty quick.