It could be a hemipenile prolapse or an intestinal prolapse. Either way, you should take them to the vet. There are several home brew remedies such as sugar water and Preparation H that can be attempted if is it's the hemipenis. The success rate of these is not very high though. In either case, it's very important that the exposed parts be kept moist until you can get to a vet.
Hi pigslayer ~
Are these two female leopard geckos on sand? Are their crickets appropriately sized?
I once had a mature Oedura castelnaui (northern velvet gecko)who was on a 50/50 Reptile Jurassic Playsand/peat moss mix ingest a wee bit of sand and immediately prolapse. She recovered only to prolapse again a few months later. She has been fine now for years. I think I was the problem, spraying at the same time as I fed her. After reinsterting the intestines my vet recommended: CatLax to her lips 1x/day, tepid water soaks 1x/day of about 10 minutes--don't overdue, and Gerber's Chicken Baby Food till all the sand was passed---a couple months. The first time the prolapse was less than the second. Sugar water did not work very well. The vet did not have to take stitches.
Sorry to hear your females passed away. On the recent one whom you soaked: When you found her dead, had she reprolapsed? I have heard that crickets are a better source of protein than mealworms and also that mealworms might be hard to digest. That might be a factor. Try just feeding gutloaded and dusted crickets. At what temp range have you kept these leos?
For young leos who are not skilled hunters you can cut off the back legs of the crickets at the "knees". That will slow them down.