A roll of HP5+ I processed the other day shows a strange spotting or mottled pattern especially noticeable in the sky areas. It is not very apparent on the first two frames of the roll, but appears pretty much on the rest. I did do something different from my usual processing--I used stop bath instead of a water rinse. However, a second roll (I believe it was on the top of the two) of film came out pretty much as expected. Two different cameras, but the one with the problems has not given me negatives like this before. Any idea of what went wrong here? I am attaching an example of the problem and an example of a frame from the second roll processed at the same time, same tank. These are quick & dirty scans, not cleaned up.