Smell when toilet flushes
I have a two story home about 3 years old. The problem started about a year ago with the upstairs toilets. Then included the downstairs toilet. It is a septic smell . The toilets all gurgle and burp when flushed which of course lets the smell burp in. I've snaked all the vents today and find no cloggs.There is a unfinished shower on the second floor that I'm sure that the trap is dry. But no smell through drain. There is also a unfinished shower and bath group (toilet, sink ) in the garage which is below the first floor plumbing. These traps are dry also, but again no smell. Smell only from the toilets? What to do next?