Micro-reticulation in the grain??
A) How are your temperature controls holding up during processing? Are you certain that you are holding the temperature to within 1 deg. C. from the time you pour in the first water till the time you hang it up to dry?
B) How are you storing the film from before the time it is exposed until it is finished processing? Can you be sure that the film is stored in stable temperature conditions from the time it is exposed until it is finally processed?
Not an authoritative answer but that's my guess...