I have a Kohler Santa Rosa toilet circa 2013. Water only fills the tank about 20% of the way - to the bottom of the center tube. I lifted up the center tube and noticed a red, possibly rubber, ring dangling off the bottom. I suppose this is the sealing between the tank and the bowl. Since there is no longer a tight seal, the water constantly leaks from tank to bowl.
I tried to remove the whole center tube to attempt to reattach the sealing, but I was prevented from completely removing the tube due to it being stopped by this disk thing. This "disk thing" is usually connected to the white tube, but I disconnected the tube during this repair. What are my options to repair the sealing if I can't get good vision of it and can not comfortably maneuver my hands around it?