We had a similar situation and put a tri-fold lawn chair with a clear shower carton and sturdy items on top the curtain to make sure it wouldn't blow away in gusty winds and scare Mother Cottontail away. 'Tis Great news that you see her returning.
Thank you for giving them every chance of survival until they can quickly hop to a more protected (dry) area.
A mother cottontail built her nest in the front yard so we constantly monitored. We have vagrant dogs, and crows, hawks, carnivore/omnivore mammal wildlife including humans who let their cats roam.
At the wildlife center we often rec'd or heard about drowned babies during heavy rain periods. One of the group of e/c's in my care did not survive when they came in from a cold & rainy situation.
Thank you for keeping watch ! - and am hoping they get the very best chance of survival once enough colostrum is rec'd from mother's milk jugs and they can hop to a safer, protected area (void of diurnal/nocturnal predators). Momma Cottontail came around to nurse when she sensed no predators would be around.
The babies are still here but they are just about ready to go. Sometimes when I’m throwing out my garbage I see mom feeding them. The other day I was walking to my garage and she was right by my garage door and I thought she was gonna do what rabbits do and high tail out of there but she just stood there without any kind of fear. I hope she knows I’m just here to help and not harm them. I would say maybe one or two more nights the baby rabbits are gonna be adults and be exploring on there own!.