Soft stools from meds or stress??

I know I only brought my lady home Friday, but I'm still concerned. She had diarrhea at the shelter, but I thought the vet visits would have helped with that. Her anus is still very red (can't get her to sit long enough for a close examination) and she hasn't had a solid stool yet. It could be one of three things:
1) stress - I know the change in environment does a number on some cats' digestion, and I have seen her 'hiccuping', don't know how else to describe it, though she hasn't vomited at all (thankfully);

2) diet - I haven't made any significant changes yet, I'm feeding the same dry food and the same brands of canned food for now, but the other thing may be:

3) Medication - she had a tooth pulled and I've been putting her Clindamycin drops in her canned food to get her to eat it. Does anyone know if this is a typical side-effect for this medication? Thanks in advance.

She has really been through it, and the diarrhea can be a combination of all the stress she has been dealing with. I would check her to be sure she stays hydrated, and just let her rest and get better.

(the pinch test) take a bit of her neck and lightly pinch or tent it. Release, if it goes back down to normal within a few seconds, she is hydrated, if it stays up in a tent position, she needs fluids and a vet's intervention- unless you are skilled at giving subcutaneous fluids.

Thanks, MA - i haven't seen her drinking anything, but the dish has been getting low, so I know she's had some, at least. She's still active at least, and seems happy when I pet her. I'll just try to be patient and keep an eye on her. Never realized the pinch test worked on pets, too! thanks for your patience with us first-time parents! )