Never seen anything like this. Arista 100 (shot at 50) developed in split 23, fairly fresh (about a month old, well within capacity) normal except somewhat shorter time due to temperature (about 72). Water stop. Fixed in TF4.
The B side, developed in straight Xtol, was completely normal.
Dumped the developer, which appeared normal too, greenish after the Arista.
Shoulda used caffinol.