Sandy: I will try the sulfite as my slowest achievable rotation is 28 rpm (knob turned all the way down) - what constitutes a "pinch or two" in a ~310 ml working volume? I have not seen this problem with any developers in recent years (not since the old GAF tanks with the twirly thermometer that were used where I used to teach) and certainly not in my Jobo tank until this episode.
I will try once more (sans sulphite) with a larger volume in the tank (BTW Ed, it's a Jobo 2523 with two reels), then the sulphite, then on to int. agitation in my old Nikor steel tank.
Thanks for all you input folks.