I've scanned both b/w and colour negs in the past without this issue. One picture from the Tmax roll turned out good. I've included it here. It's not the greatest image but it does show a proper or acceptable result, so I don't think it's a scanning issue...is it possible that I did not agitate correctly? Perhaps I created too many air bubbles? I made sure to tap the tank after every cycle but maybe I was too vigorous during agitation? How would 1 photo out of 24 be ok and the rest the same?

My ISO was set to 400 for the Tmax, I'm positive of that. I'll need to examine the negatives more carefully. I don't own a loupe buy I imagine a magnifying glass would do? I'll try making some prints to see what I get.