We had a surprise litter (thought we had 2 females). She didn't feed them, so I took them and have been feeding them. We have 2 left of the original 8 (one was stillborn though). One of them has a huge, swollen, soft, mushy, red belly. It is still eating well and pooping and peeing. Its belly just keeps getting bigger and bigger. I tried gas drops, but the belly didn't go down. Any ideas?