Maybe definitely is too strong a word, but since the water flow and lighting in the sump and tank are different, the only thing that's similar between the two places are the water or something in the water. So, it's reasonable to say that's where the problem is.
My Xenia started to look really grumpy a few times, only commonality between those times was the alk dropped, but it was much lower than 8.1. Down near low 6s. Bring the xenia over to my place, I'll look after it for you.