I have two toilets in my home, and they flush very slowly. The bowl is first filled with water and then it slowly goes down. The problem started first with one toilet and then it was the other as well. I have put drain chemicals to no avail. I have pumped the toilets many times with no good result. I have put water pressure on the toilets using a hose without results. I have called a plumber and he could not fix it. Please let me know what could be the cause of the problem.

Is the water level in the tank within 1/4" of the top of the overflow? Can you put a standard flapper on it? Does it have a low flow flapper? Is it on an offset flange. Is the wax ring squeezed in under and in the flange? Is it an eljer? Is it a roundfront?