When you have this kind of reaction with your toilets when an appliance or shower is draining, there could be a partial obstruction in the drain or sewer in your house or apartment. There also could be a partial obstruction in the vent stack that is not keeping the vent from doing its job to maintain atmospheric pressure within the drain waste and vent system. My recommendations are to cable the lines and have the vent stack and building drain video inspected to ensure the integrity of the systems are up to code.