After I plunged my toilet, there was a leak to the downstairs ceiling. Could this be a wax ring issue? It doesn't leak when I flush afterwards
Yes, that could certainly be a wax seal issue. I've resealed a number of toilets after people had plunged them. It usually happens because the flange is installed below the finished floor so the compression on the seal is compromised. If the blockage is below the flange, the pressure exerted from the plunger can easily blow through the wax seal. You won't see a leak when you flush because the water is going down to the ceiling of the floor below. You should think about resealing that toilet as the problem probably won't fix itself. Check the position of the flange, it should be installed on top of the finished floor. There are flange extenders if needed. Good luck and stay safe out there.