My hedgehog poop mushy after he changes food and ate a tiny piece of tissue

Hi I'm new to hedgehog parenthood and i have a baby hedgehog, i adopted him at 6 weeks and now he's around 7 weeks old, i change his food and the breeder forgot to send me his regular food, at first he poop normally but when i clean his box he got curious with a tissue and decided to bite and as i look at the tissue there's a tiny piece were missing, after that his poop is mushy and one time i see a slimy one with white thing inside it (I'm sure it's the tissue because i didn't see it in any other poop).

how long it'll last because I'm getting worried, and the nearest exotics vet is like 20Km away from my house😥