Mouse might have something wrong with him???

A few weeks ago I got a mouse from the pet store who was being sold as a feeder. I bought him as a breeder so I can breed my own mice to feed my snakes. I honestly don't know how old he is but he seems to be full grown. Since I've got him he's sat at a steady 24 grams.

So today I was cleaning his tank and I noticed some red squishy and slightly sticky red things in his tank. They were about the size of a dime and sort of resembled fruit, like grapes, that we're slowly rotting. The best way I can describe it is that it looked like a dried appercot. Except red and really small. I found 3 in his tank and I can't figure out what they could be. I don't feed him fruit so that can't be it.

I dont know exactly what kind of mouse he is. I did some research and I figured he's either a recessive yellow or a lethal yellow. I also read that recessive yellows are known for devolving tumors. Could that have something to do with it?

i posted this as soon as a noticed those things so I haven't yet noticed if he has any behavorial changes.

If you know what this is please let me know!

I have no idea what's going on with him but either way, I wouldn't breed him. If he may have a legal gene or a gene that can cause serious problems I wOuld not breed him. I also didn't breed a mouse that's having a serious issue like that for precautionary measure.
Would you say the gross things looked kinda like blood clots? Or bloody stool(a bit diarrhea looking, maybe)? Get a picture maybe?

I don't know what blood clots would look like, but when I saw them that was the first thing I thought of. They are pretty big for a mouse's size so I'd be surprised if they came out of his body. I don't know how to upload pictures from my phone though