Max…Check the valve beneath the left rear side of the toilet, and be sure that it is all the way open. If it is open all the way, check to see if there is any debris in the line or fittings that is causing the problem. If that doesnt help, shut the water off to the tank, and disassemble the diaphragm valve in the ball cock to determine if there is a debris in it that can be causing the problem..Bud……..Merry Christmas… Suncoast Plumbing… Sunny Florida…