Last night while my washing machine and sink in the master bath was running, my master toilet started having air bubbles come up. Then this morning while I was showering I heard bubbles again, and the shower was draining very slowly. After the bubbles occurred my toilet in the master bath and powder room completely drained of water in the bowl and tank. What is happening?
Pretty sure a vent pipe (the one going through the roof) is blocked. There should be a vent pipe coming off the main drain stack, perhaps not obvious in a multi story home. Birds and other critters are sometimes the cause
Vent blockage means air is reversing through the toilet trap, removing the protective water (which keeps sewer gas from entering home).
Water emptying from tank may just mean a leaky flapper, though this is unlikely on 2 toilets simultaneously.
A visit from a plumber is in order.