Hello,
I’m not sure if it’s the angle of the photo or not, but your kitty looks like it’s upper mouth and general face area is swollen and really distorted and does not look typical.
The brown/reddish color you describe reminds me of exactly how dried flea dirt (blood) looks. So make sure that you examine her carefully with a flea comb to see if that is an issue for her.
If she was an outside “feral” cat, be sure to get her tested for Felv/Fiv as well as a vet checkup to rule out upper respiratory infections, a rabies vaccine and distemper vaccine and spay would be good too–if you haven’t already done that. I’d take a trip to the vet to have her mouth/face examined.
Good luck!
~kelly
Get him to the vet asap blood in the poop is usually a sign of parvo