Ok. Relax. I figured it out.
I started reading (again) in old bromoil books. Then I stumbled upon the notice about how important it is to wash 'very thoroughly' after bleaching, because only the 'smallest traces of dichromate' can cause an 'overall and random tanning of the gelatin'.
oh-my...
I was dumping them straight from the bleach into the fixer.
Now, doing the "several colplete changes of water and so on" routine before fixing I am not only having no stains anymore, but also much better contrast rendition. Especially better seperation in the shadows.
Thanks everyone for thinking about a solution to this and I hope it helps anyone.