I have a three level condo. When the master bathroom on the top toilet and shower drain they are draining into the mid level toilet and overflowing the toilet. The mid level toilet is a very slow drain. I have a second toilet and shower on the top level that have no problem draining and no issues with the basement bathroom. I can't figure out where between the master bathroom and toilet mid level where the blockage is.

I have a second toilet and shower on the top level that have no problem draining and no issues with the basement bathroom.

That toilet and shower are on a different drain line from the other toilet and shower.

You have a partial blockage between the mid level and the lower level, assuming you have no problem with lower level.. Pull mid level toilet and snake the line. Put out enough cable to reach the lower level plus 20 ft.