I do the same thing with fiber paper. Develop with LPD, water stop, TF5 fix 1, TF5 fix 2, then hold in water till the end of the session (usually an afternoon), then transfer to vertical Gravity Works washer. I've never seen this either. Some of the above posts suggest spent stop or fix, which can be avoided with 2 baths (there are many threads on this forum about that). You don't mention any brand names, maybe that would help.
This is not normal for paper as far as I've ever used it, but as someone else has pointed out, if you're using indicator stop, it's either dead OR the ph of your fixer is sufficiently off such that the residual stop bath is indicating purple and bleeding over.
Stop worrying about grain, resolution, sharpness, and everything else that doesn't have a damn thing to do with substance.
12 Feb 2012
Thank you to all for your comments and suggestions. I also thought the purple color might be coming from exhausted fix, but when I noticed this with fresh fix (film strength) I knew something was "off". I mix my own fix, and recently began to consistently measure the pH. It is not as acid as I would like it to be. So comments about indicator stop (Kodak) carry-over are very relevant. (#1 thing to look into) I use city water to mix all my chemistry.
I have been printing with RC for many years. I have also soaked paper before a final wash for as much as 20 minutes with little to no delamination problems. When it does occur it is always at the corners.
Bdial asked about "using the same fixer as for film?" The answer is no, but I use the same stop for film and prints. Probably not a good idea. (#2 thing to look into)
The interesting thing is that the color does not seem to effect my prints adversely.
Thanks again to all for you thoughts on this topic.