I'm guessing that you have a clog in your main drain, not the toilet. When I had a similar situation (noticed a shower floor which is in a lower room was dirty, even though I hadn't used it in months), it was my main drain almost obstructed by root infiltration. It took 70 feet of snake/cutter from an outside cleanout to clear it (under the middle of my driveway). Eight years later, repeated. I probably need to get it fixed rather than snake it, but $2k + to have it done, so I'll try snaking a couple more times -- $90 every few years isn't so bad.
I've tried drain chemicals a few times over the years, not one time with any success.
There should be one or more cleanouts that can be snaked. Maybe the obstruction is somewhere easy and close, maybe not. My previous house had a chronic, but easy to snake, shower drain that I had to snake every few years. Bad install/tight turn.
You should probably be posting this in the drain cleaning forum.