Aquariums: Puffer throwing a fit/pouting

I have a topaz puffer (Dichotomyctere fluviatilis) and recently we upgraded from a 30 gallon tank to a 50g. This guy was SO happy in the 30 but just outgrew it, so I put all the same stuff in the new tank when it was time to switch and all of the parameters matched exactly. Word for word, bar for bar; same plants and rocks, same tank mates (hermit crabs), same filter, same corner of the house. I added a few more plants into the tank obviously because there was more space. Originally the puffer say around in the regular corner under the usual rock, but I noticed it wasn’t as excited for food. It’s still eating but I kinda have to shove food in its face for it to realize and eat it. I’ve also been having issues specifically at night, where it can’t seem to see the food, I have to attempt with all lights off- but during the day the light isn’t an issue at all. Basically after moving this fish from the 30g to the 50g it’s been sitting on the bottom of the tank, kinda moping around, shoving its face in a corner and side eyeing me. Like literally pouting or throwing a fit, and this fish IS dramatic like when I get the bucket for a water change, he normally sinks to the bottom gets all upset and it normally only lasts a day at the longest. It’s been about a week now and he still mopes around the bottom and hides in a corner, I’ll attach a picture if I have one on hand. When I first got him he threw a big fit what warranted his first tank upgrade, and he LOVED the new tank. So I have no idea what happened this time and I’m started to get concerned. Like I said he still eats, I just gotta shove it in his face- like stick my arm all the way to my armpit in the tank. And occasionally I get a little second where he acts like his old self, but the dramatics are high this time. I have speculation he might be constipated? He normally will not stop eating if you don’t stop giving him food, but he outright refused shrimp the other day. So I gave him clams and I’ve had better luck with him chowing down that, but even so he’ll only eat one not two. I haven’t seen him poop in a while maybe like a week but I haven’t seen him poop very much total so I’m not really sure how much of a factor that is. I’m just worried and have no idea what the issue could be. Like I said I’m guessing maybe constipation, but this guy seems like a completely different fish. Like he used to dart out to the front of the tank when he heard or felt (whatever it is) the door open and when I had my hand in the tank he’d come right up against me. But now he just hides all day, and feeding is hard, and he seems scared of me. I know it’s irrational but I feel like my fish hates me! Thanks in advance for the advice.

TLDR; I upgraded my topaz puffers tank and it’s like he’s a completely different fish. Went from very social and out in the open to very skiddish and always hidden. I’m thinking maybe constipation. All parameters are exactly the same as the old tank, only difference is behavior. Still eating, looks okay, there are moments when it acts like the fish I know, but it’s significantly less than before. Any help is appreciated.