DO NOT LET MOTHER RABBIT NEAR YOUR OTHER RABBITS UNTIL A QUARANTINE PERIOD HAS EXPIRED.
You are going to need to get the mother rabbit checked out and isolate her from your other rabbits. While cottontail rabbits cannot breed with european rabbits, rabbit diseases can cross over from one to another. You may very well need to give the mother rabbit a course of widespectrum antibiotics and a widespectrum antiparasitic.
If you have already let mother rabbit near your other rabbits, a prophylactic treatment might be needed for all of your rabbits.
It is also worth noting that, because the gut flora of european and cottontail rabbits are almost certainly not the same, the milk and cecetropes provided by the mother may not provided what it needed to seed the intestine.
Finally, if you have any dogs, you may want to keep a close watch on them too. Wild rabbits can carry parasites in their poop that, if eaten by a dog, can infect the dog and cause serious illness.