(there was a url link here which no longer exists)
This thread has some good images of reticulation, and discussion. What I can't understand is why in this case the effect is so restricted in spread, and across films to same degree (needs confirmation from the OP). The reticulation, classically as in the examples linked, is all or nothing. Of course it would be possible to "freeze' the effect as it emerged but to do that repetitively and consistently is a stretch.
In the thread quoted wash water temperature variation is a issue, again the OP needs to confirm the washing technique and stability of that temperature.