Yep my experience bottom up is too high alk or too aggressive carbon dosing or combination of both. Lower to 7dkh and see what happens.
Lights left on usually causes tops to burn so unlikely the cause in this case.
DG already said it, I used to run alk at 9-11dkh with no visible stn; sometimes higher... But drop in a couple drops of vodka or vinegar.. The first thing I'd see is nice polyp extension and the second would be signs of stn. Stopping carbon normally took care of that along with slowing or stopping alk for a couple of days. But when the colonies got large the alk would fall very fast... Something to watch out for
Alk is in the 7.8-8.0 range, I will drop it down slowly and see what happens. No carbon dosing at the moment, I was running some GAC in a filter bag in the sump pretty aggressively when I was trying to get my skimmer to calm down.






