We have a back to back bathroom set up that is always giving us troubles!slow flush from one toilet and the other toilets bubbles and overflows ,when I plung it it sends all water back to other toilets and it overflows and bubbles ,I've used a snake and it seems to go up the vent stack ,these are newer toilets and newer seals other toilets and drains work perfectly .have opened check site bath water flows by and sink water flows by just no toilet water ?

Helllo, sounds like the drailine is plugged, so you need to get the snke to go downward t get to the problem. You may need to get a plumber to help you if there is no access to the drainline between the two toilets.

you may need to get a plumber to help you if there is no access to the drainline between the two toilets.
But there is access to both toilets through the roof vents. You're snaking from the wrong end. Send a sewer snake down each one of the lavatory vents. Put out enough snake to reach the base and 30 feet more. Good luck, Tom