Start treatment right away and isolate him. If it is dropsy, the sooner it's caught the better chances are for recovery. Unfortunately dropsy has a very low cure rate after the scales start pineconing but it's always worth trying. You could try the epsom salt bath to relieve the bloating (no more than 1/4 teaspoon per gallon) and keep a CLOSE eye on him while in the bath. Remove him at first sign of distress. Some Bettas have a bad reaction to it (Phlox nearly went belly up after 8 minutes) although from what I've heard, most will tolerate it. You can do this for 15 minutes twice a day. It is very stressful for the Betta but if it relieves the bloat it may be worth it. If he reacts badly don't try it again. Try to use a cup to scoop him out of the tank instead of a net if you can. It's less painful and traumatic.
I don't know what else to tell you except make sure he has clean warm water and no rough gravel. Use a bare tank or glass marbles as he may spend a lot of time on the bottom.* I hope he recovers. I'm going through a hard time now too with Phlox. I'm certain he doesn't have dropsy as his bloating has gone down with fasting but he still looks pathetic. Why do these sicknesses strike us all at the same time. It's so depressing.

Keep on eye on the cories and give them lots of water changes to prevent the bacteria from attacking them.
Try fasting Julian for two days and then feed only pea treats for a couple days. He may have a little constipation as well and with any bloating his digestive system will be stressed. Letting him clean out his intestines can only help him.