Chelsea? Dorchester? Revere? Just reminiscing. ( Grew up in MA)
There is a problem here and your landlord may need some gentle prodding because it is his problem. For a test, take a large bucket(at least 2 gallons) of water and pour it into the toilet. It should cause a nice flush. If it is sluggish, there is a problem somewhere. The scary part is if the problem is out in the main then you could have a situation where the drainage from the upper floors finds the only path gravity allows is out through your tub or toilet.