Stringer question 23' InBoard Potter built

[GetReel]

Pulled my deck up and removed gas tanks to re-coat with airplane epoxy and was poking around. I noticed that the aft weep holes near the hull joint in the 2 main stringers on the outboard side of the tanks seems mushy, but limited to the interior core of the weep hole...the glass is in great shape, I know there are many threads on this but,

can anyone verify the construction of the stringers and transom circa 1975, glassed in fir, plywood?

any chance of any other material?

I'm thinkin that I'll core drill the area out and see if it gets dryer, then seal with resin.

thanks.