I've always wondered about wet foam in composite boats and delamination issues. Occasionally you head about issues but I haven't seen a thread anywhere where anyone has pulled the floor and checked for saturated foam and standing water. I have felt that regardless of wood or composite, the main problem is foam holding water, particularly if it freezes and cracks the glass, lifts the floor, etc... It may be worth cutting a hole in the floor in that area between stringers and digging through the foam to check if trapped water may be causing the delamination. If you find it dry and no delamination on inside of stringer just patch the hole and bond the bilge side where you have the issue.