Recently we noticed a bad smell coming from our downstairs bathroom. When we investigated it further it seem that there was some leakage from base of the toilet. So had a plumber come out, took out the toilet, and informed us that the wax ring had failed. So he replaced new wax ring and reinstalled the toilet. The smell never went away and it actually got very bad. The smell gets especially bad when the temperature outside gets very hot. The smell is like a sewer like smell and its very bad. The whole bathroom smells bad and we can pinpoint it coming from base of toilet since we are unable to smell it from sink or bathtub. This bathroom does not have a fan, just a HVAC vent and window. What could the issue be here? Is it some sort of blocked pipe? blocked vent?