Over the last few months I have noticed 3 of the 4 toilets in the house are not filling the bowl where they used too. I know this because we are on well and septic and have very hard water and can see where the original line was by a small iron ring around the bowl. Two are 2 years old and one is 15 years old. I swapped out the guts on one of them but no change at all. What I also notice is this. After flushing the bowl, it gets to its (new level ) pretty quickly and then continues to fill for another 20 or 25 seconds (I can see the water coming into the bowl) but the water level never gets any higher. The water is going somewhere but not in the bowl. Is this normal? I originally thought it was maybe a clogged sewer vent. I ran water with a hose down it but nothing.. Same thing. Also, I am not getting the gurgling sound in the toilets people talk about. Someone else told me a partially clogged sewer line. Anyone have any ideas? Or need any other information? 3 different plumbers and 3 different diagnosis'. I would like to at least be able get some opinions so I know which way to proceed before this turns into a nightmare of tearing down walls etc... Thanks!