your post is a delight on several levels
Yes, I probably have to tentatively agree that apurensis have more or less same appetite year round, if one corrects one's expectations for the usual water temp effect - the warmer the water, the higher the metabolism, the sooner the hunger returns.
Yes, I too am worried a bit at the lack of normal beastly appetite from Jello. It could be the food size. Maybe she doesn't want to bother with 1.5ft mackerel having been used to 6"-8" herring for many years. Jello did take two finger mullet and a mackerel tail in her more or less normal gulping fashion lately but Thug goes bonkers when he smells food and doesn't find it, he then bumps into Jello and tries to get at the food through her mouth or gills, so yes, there is a stress factor for sure. For Jello's sake I may have to move Thug, or actually it is 100x easier to move Jello as she is so chill vs Thug who fights like he is being deep fried.
I doubt the newness of the offered fish.
I did see and report that Jello seems to not be as happy in that 240 gal, perhaps because she is longer than the tank width, or could be because of Thug, or both. But Thug dials down his antics and activity 100x when no feed smell in water.
Thiaminase has been on my mind a lot too, so everything I give her I make sure it is fortified with B1 and Vitachem.
Once in a while Jello does bite Thug, usually inconsequentially but sometimes leaving a good mark, but not persistently or viciously, no intent to injure or kill whatsoever. Thug never answers. Only bites her mouth and gills when she's got food in her mouth and he doesn't.
The way the paroons have been in the 4500 gal, I cannot place her back there in good faith that it could be alright.