If the bolts had deteriorated it would certainly have been visible when you removed the plywood, which was likely at least damp. If they looked good where they were buried in the plywood they will be good lower as well. You are over-thinking this. Adding extra bolts will not add much anyway as they will not have as solid of an attachment as the originals nor hold as much load as the originals.
The wood was damp throughout but there was no "puddling" of water around the bolts, just dampness. Maybe there is water laying in around the laminate and next to the bolts.