Since they are new gliders I would take them to a vet and get a check up. see
if they have any illness. that is your BEST, FIRST STEP.
gliders groom themselves and each other. one glider is a ALPHA OR LEADER OR
colony BOSS MAN. This is natural, drop the thoughts of bullying. My alpha Gus
will sometimes chase, nip at or look like he is attacking another glider. there
is no injury and seconds later they are fine, sitting together with me.
BUT you need to keep and eye on them, feed them good food and have playtime
and things for them to do, sometime gliders do kill cagemates, but some over
grooming might not be a big deal, so see the vet and get some good information
from a professional please.