Weak Flush?
The new toilets in the U.S. that are required now days are known as water savers, a good idea, but some don’t do a very good flush job. If yours is the common type check the water level in the tank, Make sure that it is high enough, You need lots of water usuly for the fixture to work properly. Another thing you can replace the new style rubber flapper in the tank with an old style flapper.