Checked them at 6pm = 3 hours after lights come on.

BD1 was at 5.1 PH and 1368 PPM
BD2 was at 5.0 PH and 1428 PPM.

Decided I was pushing them too hard, and drained res at 10pm. Refilled with RO water and adjusted PH. Due to bubbler design, a little residual solution remains in res and affects final PH/PPM.

BD1 is at 5.8 PH and 306 PPM
BD2 is at 5.8 PH and 511 PPM.

Haven't seen them yet today (12/30) so I will check and post back. Yesterday they had good growth, no nute burn, and were filling the screen pretty well. Update to follow.