When I got home from vacation 3 weeks ago, Vitara wasn't feeling well. She was pretty lifeless, acting kinda wierd, and had no appetite. I kept an eye on her for a few days, noticed she had white, stringy poop, and decided to treat for an internal parasite. I gave my mom the name of the recommended medicine for internal parasites (starts with an M, can't think of it right now!) while she was out by Petsmart. She wasn't able to find that, so she picked up (something-clear?) fizzing tablets, for internal and external parasites. I followed the instructions- 1 dose, and 48 hours later a 25% water change and another dose. Nothing's changed. I occasionally put up to 3 pellets in right near her to see if she'll eat them, and she shows no interest in them at all. She actually backed away from them the last time I tried it.
It's been 3 weeks since I've been home from vacation, and I don't believe she's eaten once. Is that possible?
What do I do? I'm at loss...

What do I do? I'm at loss...