Hm, this was basically the answer I got when I asked what the difference between the "new" RA-4 papers and the old ones is. (keep in mind that this was from a reseller, not Kodak or Fuji)

More sensitivity whith that shorter exposure times, but the tradeoff was that the paper is harder and the sensitivity gap shifted.

I dearly hope that the blue cast i observed was from something else but the safelights (which have worked on the same settings in the same darkroom without any cast before)

will be after christmas that I fire up the Thermaphot again, but will report back......