HELP! What’s wrong with my hamster?

[Biscuithamster]

In the last week or so I’ve noticed a red bulge coming from my hamsters bum (I think). It’s a girl hamster called biscuit. Today I have noticed it now looks a little wet- possibly diarrhoea? But not major.
She seems her fine happy self and doesn’t appear to be in any pain or discomfort. I cleaned her cage out last night and I noticed she wasn’t busy rearranging it all like she normally would, she’s barely touched her treat either. For a while I’ve noticed she doesn’t eat as much and is quite selective with the food she takes out of her bowl whereas before she used to empty her bowl and be waiting for more to be refilled. She seems to be drinking quite a lot, and sleeping more. She is 2 months away from being 2 years old. Please help. I have a photo

[souffle]

anything like this plus a change of behavior does need a vet check. It could be a number of things like a prolapse of the bowel or womb or a tumour so I would have her seen as soon as possible. She is getting to be quite elderly now for a hamster so these things can happen.