Soft sticky poop can be a sign of an illness or parasite. Chins hide illness until they physically can't anymore, and are at death's door pretty much, so not acting sick doesn't mean not sick. I would stop all treats including the rose hips, the hay and pellets should have the nutrients the chins needs, they don't need the vitamin C. To firm up poop you can also try pulling pellets and just giving hay for a day or two (some people have had luck with that, others not so much, but chins can live off hay alone so it wont hurt). But if it doesn't improve a vet visit is needed. The vet will need to do tests on the poop to know what the problem is, there is no way to tell just by looking at it whether you have a virus, bacteria or parasite problem and each require a different treatment.
The fact that you are having a possible peeing issue (you mentioned in another post) and a poop issue I would take the chin into the vet anyway as soon as possible, as in like tomorrow morning to get checked out. It sounds like something serious could be going wrong.