1984 is not very old. Old, yes, but lets not bury the thing in the cemetary, yet. Consider perhaps that your sails are getting tired, too. Are they 1984 vintage as well? Age brings sag (sorry ladies). It would seem that you aim not to sail a beat to often. Did you sheet in especially hard to get back to shore out of necessity, surpassing your normal amount of effort? Did you change your rig and create more rake (or maybe soneone else did)?
As far as your hulls go, rap on them with your knuckles. just kock on the hulls all over and listen for really wild changes in the sound. If you are knocking along the hulls from stem to stern and you hear a nice solid response and then in some particular spot you get a uninspired thunk, you may have some fiberglass problems. Before jumping to any terrible conclusions, do this to both hulls and listen for symmetry in the sounds from left hull to right. Don't confuse bulkeads or stringers with bad spots (do 5.7s have bulkheads or stringers?)
Just my $0.02 worth