From one of the links I gave you:
What can you do if too little water comes from the tank to flush the toilet bowl clean?
Step 1: Check the water level in the tank. It’s probably too low. If the water level doesn’t reach within 1 ½ inches of the top of the overflow tube, bend the float arm up slightly to let more water enter the tank.
Step 2: If the water level is correct but there’s still not enough water coming from the tank to clean the bowl properly, the problem may be the tank ball on the flush valve seat the bottom of the tank. The ball is probably dropping too soon because the guide is set too low. Raise the guide, but make sure it stays in line with the lift wire. If the guide and the wire are out of alignment, the tank ball will not drop straight into the valve seat opening, and the toilet will run continuously.
Step 3: Look for other cause of inadequate flushing. The small ports around the underside of the toilet bowl’s rim can get clogged with residue from chemicals in the water and prevent a sufficient amount of tank water from running out into the bowl. A small mirror can help you examine the holes, and a piece of wire coat hanger or an offset Phillips screwdriver—if one is available—can ream out any clogged debris.