Sounds to me like you are having paper fog from something...either the safelight or the exposing lamp. I had this happen with MAS Amidol formula when I developed the paper for a longer than normal period (cold darkroom temps)...this was with graded Adox and a Zone VI safelight on high (graded paper)setting.

I finally decided it was the combination of the time in developer in conjunction with the higher safelight exposure. I cut the safelight intensity and came back down on my development time and the problem was eliminated. Higher ambient or developer temperatures would tend to exacerbate the problem, I would think.