I assume it was from stress, I mean just based on how he's looked. He was making a decent recovery until the move, and after that he seemed to recede and then kind of "stabilize" at a not-very-good looking state. The split happened over a month after the move, so it wasn't immediate but perhaps he was just unhappy.
As far as water quality goes, I keep it as good as I can, at least the things I can test for. Salinity, pH, Alk, Calcium, and Magnesium are all stable and in good ranges, and I haven't let nitrates get over 5 yet. There may be something else amiss with the water, but I don't have any visibility into that if that's the case
One thing I'm optimistic about, is that now that he's moved (I gotta get used to saying "they" instead of "he" now lol), they can situate themselves wherever they want once they come back out. If the light was a problem before, at least now they're moving about and can get to where they are happy. Keeping my fingers crossed!