New kitten has unhealthy looking hair and a shaved back?

Hello! i just got a long haired kitten from

my local shelter, and i noticed his hair looks a little mangly and his back was shaved but no surgery scars that i can see. I assumed the hair looked that way because it was matted, and thats why his back was shaved, but when i brush him its not matted, just unhealthy. It wont let me put photos but it kinda looks like clumpy, but doesnt feel particularly oily.

ive heard this can be common in shelter cats from stress and diet, so just wondering if you guys experienced this?

Any clue what the shaved back could mean? and the hair?

Im worried he has some underlying health issue the shelter didnt say/test for, because he looks a little underweight, (but that might just be because his back is shaved) and the fur of course. Going to take him to the vet soon for a check up, but thought asking here would be good too.