Okay . . . both baths have power lite/vents which come with built inif you have one fan pulling the main line its good, if you have fans in each bathroom pushing into a combined vent no good, as you can force the air from one bathroom into the other..
baffles to prevent back flow. and the feed duct from each to wye
also has a baffle. thus my overkill.
A baffle is standard on all bath power vents from box stores.