Why does my ferret have diarhea more often than her brother?

Why does my ferret Kiwi have more bouts of diarhea (probably 5 times per year) than her brother Rascal? He's only had it a couple times in the 4 years we've had them. They go to the vet for their distemper shot and get a checkup than, so I dont think anything is horribly wrong with her, esspecially since she is at least as hyper as him, and usually even more hyper. Also, can it hurt ferrets to give them Pedialite when they don't need it? When I see diarhea in the litter box, I immediatly make both of them have some, since I dont know which one did it and I don't want the one with tummy trouble getting dehydrated. I give them pure Pedialite with a little bit of their ferret vitamins mixed in so I can get them to drink it. Its really funny after they have it bc they get really hyper. Its kinda like a kid on a sugar high. But whats not funny is Kiwi's persistant tummy troubles. Thanks to her sensitive stomach I get to sit up all night making sure she doesn't get dehydrated. Any advice?