Well, almost a day later and they're back to normal. Actually, this morning one of my frogs who has a leg problem (when they try to swim quickly their whole body twists, but when moving normally nothings wrong) was also floating, but now they're all back to normal. I added a bit of aquarium (epsom) salt to the tank so that may have helped. So if anybody has the same problem and sees this thread, just do add some salt and wait it out.