Run down the side of the rib with a craft scalpel , if its tinned you see a bright silver white line . If its epoxied you will get a sample of residue. How do they sound when rung ?They will sound dull if they have been glued . Looking at the photos it looks more like seepage from inside and if you can scrape it off then I would suspect this to be the culprit and the only way to stop this if the ribs are otherwise sound , would be to drill some vent holes , inject some solvent to wash out between the ribs ,drain and dry out thoroughly then seal the vents . May sound a bit amateurish but will usually cure the problem short of a full strip and relay . Of course you could just brush it down and oil regularly .
