I have two mounted, framed (under glass) 8x10s I did in the early 90s printed on whatever Ilford MG was current then - III? Both were developed in LPD, fixed in Kodafix as specified for RC paper, toned in selenium 1+19 or so and washed per RC paper directions. Both are showing deterioration, in both cases mainly around the edges near the matt, making me wonder if the mount/matt has something to do with it, but one has discoloration far in from the edge. It's sort of a pinkish purple discoloring, much like selenium toning over done but lighter (it isn't that - all I saw was a very slight cooling and increase in d-max.)
I don't know WHY they are doing this, and certainly don't claim it's anything to do with the paper. I just don't know. Mounted under glass? Something in my long-ago processing that wasn't up to snuff? Dunno. I'll try to take some close up digisnaps to post.