I've had something strange happen to my roster in the last day or two where suddenly all my position groups share the same weight. The heights have not changed, just the weights—all my RBs are now 217lbs, WRs are 198lbs, etc. I had a variety of weights on my roster beforehand.

Anyone seen something like this?

Yes, I have noticed the same thing.

They adjusted their weight to the programmed standard for their position. If they were just a few pounds away from that weight, this happens during training camp or the first few preseason games. If the gap is greater, they might adjust their weight during the regular season.