Just installed two Toto Ultimates. One is working great. On the second, the water level in the tank drops, but no water leaks into the bowl. Nor can I hear any sound of water leaking. When the water in the tank reaches the low point, rather than refilling the tank, the fill mechanism just allows water to trickle out slowly. I've adjusted the flapper valve but it doesn't help the water level dropping. I hope I haven't bought the first Toto lemon. Thanks for any insight.