I've had the same problem Connie. Everyone's advice has usually been just to keep my hands out of the water and that has worked for me. For the past month or so I didn't have a skimmer and my water was just really nasty so I didn't even get close to puttin my hands in there for nuthin and my toadstool has been opened up the most I'd ever seen it open up. Also another thing is to keep alot of flow on it so it can shed more easily. And another thing is to check and make sure you don't have any snails or anything irritating it cause that'l make it close up alot too I've notice. And umm shrimp'll do the same thing and tick it off. That's about all I can think of.
30 L aquarium, 50 lbs LR, 44 lbs LS, 192 W PC, CPR Backpack Skimmer