Best thing to do is do a search on the forum for delamination. You will find a ton of information and none of it is good. Sorry but the fix is expensive so you may just want to live with it. It can be caused by water or faulty gluing and was a huge problem in the middle 2000's. Most newer trailers have gone to a solid fiberglass cap to get away from the problem.
2007 33.5' Arctic Fox Fifth Wheel used for full-timing for several years--now sold
2011 Hideout 23RKSWE that we now use for poking around local parks
2007 Chevy 3/4 ton diesel with Prodigy Brake Control