Concerns About Gill Loss

Hello hello!

So. A couple of days ago, it was noticed that my axolotl was lethargic and not wanting to eat. I'd been away petsitting, so my family was looking after my lotl for me. I was able to get him to bounce back easily, and everything seemed normal.

Admittedly, I'd had him in a tank that was too small, so I used my earnings to buy him a proper sized tank. He's been in the new tank a total of 48 hours, and to my alarm, this evening his gills seem to have been "shedding" off! They're literally all floating around... I've not been doing anything differently, pH and Ammonia are all in the right parameters, the tank is a good temp. I feel so bad, he really had spectacular plumage!

The only thing I think might be different is the filter. I needed a new one, and the tank came with one so I gave it a go. I'm not as fond of it as the old one though, so I'm going to get one for the new tank size from the other brand. I know at the very least this one creates a bit stronger current.

Lotl is swimming around and acting normal, eating still. I know if I can figure out what went wrong his gills will regrow, but I'm super concerned! Anyone have any ideas?

The shedding sounds like what happens after bad water conditions to me. That would mean there's nothing wrong with your current tank, but with the tank the axolotl came from (and now he's in a tank with fresh water and a strong current, the irritated skin and mucus layer is dropped).
Do you know specific values of temperature/ammonia/nitrites in the previous tank?

(Also, it's not guaranteed that the gills will grow back to their former size. Since the axolotl now has a bigger tank with more current and probably a larger relative surface area, there is probably more oxygen in the water - which could mean the gills will stay a bit smaller than before.)

As far as I know, that tank was also within all the normal parameters. Maybe a little bit cooler? But not more than a couple degrees Fahrenheit.

Today he's swimming around and being active, so I feel like I probably overreacted? But it was very startling to see! Hopefully you're right, and there won't be any further complications. Thanks!