Unfortunately unless you have a vet capable of neutering (and believe its best for the mouse e.t.c) Jerry is best alone now
That said, Peanut and Nuthatch are completely content alone and I'm sure Jerry is too
I'm glad you found them, strangely to us they don't look that small in it, the cage just seems far more right for space
They had been in a duna fun with no shelves, toys, tubes or anything else since Friday afternoon/evening so its nice they've got space now