My yellow fiji is very tempermental. If I just touch it, occationally it will look like an old shoe w/o any polyps at all for a couple days. Other times I can just about beat it up and it will look normal in 5 minutes. Usually changes in light and placement cause mine to shrivel/retract polyps for the longest time. It also seems to be just as light loving as sps does although will tolerate lower levels too, just not too low like pc's.
Unless you are seeing a peeling of the surface tissue around the base or a mold-like growth forming I'd just wait it out. I've never seen one split but I would think that it could under the right circumstance. Mine usually gets buds on the sides which I can snip off. Also make sure somthing isn't picking at it if there is an area of funny tissue at the spot you think it's splitting at.
Pics would be best instead of guessing what it looks like.