I think the pipe going up must be a 3". A house is required to have at least one 3" vent The main drain there is 3". I'd redo it all, wying in the toilets separately, as well as everything else. Someone might read the code and show how it's all okay, but it doesn't fit common sense.
Is the master shower vented any other kind of way? The only way you would see any other vent is if it branches out of the drain line, and goes up. There is no other vent for the hall shower. The 2" drain for that shower is not far enough away from the main stack to require a vent, but I would have vented it anyway, since there is so much other stuff dumping into the main stack right there.
I'm not a Blum user, so someone may want to double-check those are correct. But that's $8.24/pair. Almost half the price of Rockler.