Hi,
Sorry to hear you're having such problems with your new babies ;(
Personally, I would suggest keeping them inside so that you can keep a really close watch on them. Also, the nights have been pretty cold lately, so i would want them kept warm if they are unwell (and as they're only babies too).
My 5 are out in their hutch and for the last few nights the temperature has dropped into single figures, so they've had an extra cover, loads of hay, plus a heat pad. If one of them was unwell however, i'd bring him/her into the house.
Hope things improve for them,
Helen x