I have an unopened bottle of Sulmet if you can't find any locally Peach. I would probably wait to use it though until later on unless someone around here knows for sure it is safe for an extremely young litter or lactating does. I just don't know about that part since I've never used it.
Sometimes the older kits get fur caught in their poop during the transition period and it can get matted. Once you clean it off and clip the hair around their nethers they should be okay again. I'd make sure they have hay to nibble on.
I've never dealt with GI issues in newborn kits though- their mother should be keeping them clean and stimulated when she is nursing them. Since she has been a freak when bothered, I'd probably leave them alone completely for a day and see if she starts to do her job so you don't have to keep messing with it. I know this sounds terrible, but I am also very much a believer in survival of the fittest with the youngsters. If someone is sickly right from the start and Mom is ignoring them then there might be something defective about the kit. Hopefully this is just a case of a Mom dropping the ball though and hopefully she will get back on track asap.
Best of luck!
Lauren