That shouldn't be enough to cause reticulation problems, at least in my experience. Was the film old, or perhaps acquired from a shop that may not have kept it from getting too hot in storage? I've never seen anything quite like this, but I'd be more suspicious of the film than of the developer - unless it was a really old bottle. Even then, HC-110 concentrate is very long lived, generaly speaking.
HC-110 and T-Max do not seem to "like" each other, but I've never had the mottling problem you describe. Plain old D-76 is actually the best developer around for T-Max films, any format.
When using HC-110 and any B&W film, in any format, Dilution B is waaaaay too strong I find. Weaken your solution and extend your developing times. It's a small possibility that too high a temp and too strong a solution of HC-110 *might* be the cause of your problem. Hard to say.
The image you posted is very pixilated and that makes it difficult to judge, but it looks overdeveloped to me.
If you diluted the HC110 with either high pH water or hot water (or both), that could give your working developer a significant activity boost.
Working solution was mixed at 70 deg.
My litmus paper is probably 10 years old and my garden/potting soil ph tester only works in soil. I have no idea what the ph is, but I do know the city decided to add floride. I've had other negs that didn't do this, so I'm guessing I just had a bad day. Could've been the agitation too. The image was a flat bed scan of the negative. But, I looked at the neg with a loop, and it's still bad. It's not that great of an image to fret about. I just wondered so I wouldn't do it again on something good (good neg).