7 weeks is very young. Usually you're not allowed to sell rabbit under 8 weeks of age.
In any case, you will need to be vigilant about treating this or get her to a vet immediately. Is she eating? Try to give her the exact same food she had at the place you got her--same brand of pellets, etc. Take out any sugary treats, like carrots, apples, oats, wheat-based products. Give her some probiotic. Pet stores sell a good one called Bene-Bac and farm stores sell a good one called ProBios, but if you can't get either of those, go to the pharmacy and get acidophilus capsules. Do not give yogurt or a milk-based probiotic as rabbits are lactose intolerant. Offer her an additional water source--a bottle if she already has a bowl, and a bowl if she already has a bottle, and a bowl full of pedialyte (infant rehydration drink with low sugar content but good electrolyte content).
Anything else you can tell us about the runny poos/diarrhea? Are they mushy balls of poop, or actual liquid diarrhea? What is the color? Is there any mucus?
If there is mucus, it is all liquid poo and no solids, she isn't drinking or eating, she is acting lethargic, or if the color is not brown, the bunny needs to go to the vet ASAP. She may have a condition called mucoid enteritis where bad bacteria in the GI tract build up, causing diarrhea. The toxins released by the bacteria need to be absorbed by a special drug--two options are Questran and Bio-Sponge, and the bacteria need to be killed along with adding anti-inflammatory effects to the GI tract, accomplished with a drug called metronidazole. She will also need sub-q fluids. Questran and metronidazole are prescription only. Bio-sponge is a newer product that not many people have. I ordered some to keep on hand but it is primarily used in horses and isn't commonly stocked by other vets.
Young bunnies have an unstable GI bacterial population. Starting at birth, they gradually populate their GI tracts with the correct bacteria simply by being groomed by the mother and being around her. As they are weaned off milk and onto solid food around 6 weeks, it is critical that they get the correct bacteria from their mother. For months after weaning, the GI bacterial community is unstable because it is so newly established, and it is most unstable when the bunnies are younger. The post-weaning time is important for bunnies to remain with their mom so they can get and sustain the right GI microbes. Your girl was taken from her mom a bit too early so her GI system is even less stable.
In my book, a bunny with diarrhea under 3 mo of age is an immediate emergency vet visit.
ray: Glad to hear she's alright.
