Mark
I was once a keen camper. The prospect of getting detergent on the tent fabric was worrying, it would likely strip the waterproofing. You can get a re-proofer called Fabsil from any camping supply shop, and a stronger version of this solution is made for marquees, but I can't remember its name. Based on my experience, before the waterproofer can work ALL of the detergent residues must be flushed out of the tent fabric, ideally using another special solution (I think its called Tent-Clean). I didn't do the latter operation on one occasion after an accident and the re-proofing was useless, even when done repeatedly. Anyhow, the re-proofer is tricky to apply and is liable to leave a strong watermark on the fabric if it's not spread with a consistent 'wet-edge'.
Sorry for all the jargon, but I would be careful if you've not attempted to clean this sort of sensitive fabric before.
Regards
Pete (JS2)