Chuck, I don't think the issue comes from pouring, as a stop bath after the CD step prevents these funky patterns regardless of pouring style.

My impression is that as BLIX gets used its pH rises to the point where it doesn't stop development any more. If this is the case, fogging is likely to happen. A stop bath will prevent this for good, since first it stops development at once, and then subsequent washes before the BLIX/bleach will wash out most of the remaining color developer.