I agree with cleaning them off. I would also dip them in either coralrx or a mixture of 75% tank water and 25% hydrogen peroxide (just the plain old 3% stuff you can buy at walmart). Sometimes mine will close up like that and I stick them in front of the powerhead to blow off any grot, then dip them. They almost always open back up in a couple of days after I treat them.

A pic would really be helpful if you could get one.