They may well be damaged beyond repair, but I would try washing them in the sink with some Dawn and free-flowing water. Sometimes the amount of rinsing you can get on the nitty gritty is not adequate to remove all the residue. No need to wet the labels. After the sink wash, use a regular fluid on the NG to remove tap water residues. Worth a try I think.
cleaning gritty surface noise on LPs
Back in the '70s I used a Disc Preener to clean my records. At times I, or perhaps a roommate, might have gotten the Disc Preener too moist, and the result has been a low-level, gritty surface noise on some of those old records that are otherwise in good shape.
I've tried cleaning them with various record cleaning solutions (mostly alcohol-based) with my Nitty Gritty RCM, and nothing has lessened this particular noise, even though they have worked fine with other LPs.
Has anyone encountered this problem and solved it?