Hull Concaving After Lam Job???

First attempt at a board and everything went better than expected while glassing.  Glassed in cold weather (60 degrees) using 2lbs EPS foam, and lam schedule of kevlar/glass, and epoxy resin.  After lettting it sit and cure for 2 weeks I noticed that the hull from the nose to about 8 inches back is denting inward a fair amount.  I sealed the foam off from the epoxy so I don’t think it’s that, but I have no clue.  Anybody have experience with this happening?