The tank flushes into the bowl, the siphon starts, but at the end some water backs up into the bowl. It can bring a floater or two with it.
It happens to all three toilets. So my guess is a clogged vent pipe. I haven't been up on the roof, it's been very wet and I'm no longer that steady, so I haven't looked. I'm not sure what you can see anyway. But the house is surrounded by oaks and the gutters do fill up.
So, most likely diagnosis the vent pipe? And any good strategies for unclogging?
I never did buy a camera for my tub leak, maybe I need one for this.