Odour in hammy's ball after using

[Britishhammy]

Hi! I've got a 10 month old Syrian male (roughly, he was a rescue). Over the past 2 days I've noticed a musty unpleasant smell in his ball when I take him out of it. He's used this ball for past 4 months no problem. His cage doesn't smell and when I get him back out later, he also doesn't smell. He's otherwise eating and drinking normal, usual behaviours and seems happy. I did notice a little wetness around tail and after freaking out initially, realise he didn't have any other symptoms of this. Does anyone know what this is? Thanks

[souffle]

He is probably peeing in the ball then showering himself in it. Try and ensure he has had time to wake and been to the toilet before putting him in the ball and also that he is not in for more than 10 minutes at a time then has a break for food, drink and toilet purposes.