. Problem solved, I think. I was hanging the film to dry in the furnace/mechanical room and I suspect that the fan was kicking up dust sticking to the wet film - quick re-rinse took care of that. - wipe marks of course were on the scanner - Doh!!!
Oh - the tri-x and rodinal is because I am an old guy and it is what I used to know - never a problem in 35 mm, mind you, back in the day we were not scanning our negatives. Salted, yes to further slow the reaction of the developer which will change the tonal range grain, but like salted caramel it is likely an acquired taste