Lethargic with weak back legs - but still responsive like normal when i pick him up etc

Quincy has become lethargic with weaker back legs. He's pooping and peeing the same, eating less of his dry food and looks to have lost a little weight but chomps up all the live superworms i give him. His belly felt a little cold. He is not cuddly by any means so i lowed the heat lamp on his cage to be closer to his sleep igloo and covered majority of the cage with a blanket to warm him up. Could he have possibly been on a hibernation attempt kick? I've read online this can cause a little bit of weakness... hes very responsive when i pick him up, hisses and curles in a ball then uncurls pretty quickly, which is normal. He's alert and curious just doesnt walk around much. Ate up about 8 or so whole worms, seems to be drinking water normal. I hear him moving around as soon as the lights are off in my room, he's just a little slower and doesn't use his wheel - he'll be four in Feburary 2023.

i noticed a moldy lump of pellet food under his cage liner of which i'm now on high alert to watch for again in the future until i can get him a new water bottle - the current one is leaking i now know.

Any input would be greatly appreciated and I'm very well aware this could have very well been my fault for neglecting the cage cleaning. Just looking for some help from fellow hedgie owners