I thought about it, and
@Frank the Dank helped me make my mind up. I'm sure it's my new light. It's the only thing that changed in the environment. All other perimeters all the same, RH, temp, etc. I followed the manufacturers recommended height, and settings. Crazy thing is I kept checking the PPFD and it was actually within range. But I think that due to an overpowered on board UV-A, the standard PPFD is too much. So I raised the height to where I think it ought to be, and now I'm just waiting to see how the rest of the lot responded.
This is the first time in literally years, that I've had this happen.