REQ: Need Help On American Standard Toilet

O have a one year old American Standard 'Low Consumption Water Closet' (keyword = Low Consumption). The only somewhat readable ident info on it is
9317-N 6.0 lpf/1.6gpf
I was working just fine until about two weeks ago. Now it does not want to flush completely. I don't think my waste has increased measurably, so it appears to me that not enough water is being drawn from the tank to the bowl. In fact - the thing seems to want to do the flushing action before the tank is half empty. I never noticed that before.
I thought if I could get more water to the bowl that the flushing would be increased, but I quickly discovered that even if I hold the handle down (thereby emptying the tank), the flushing action still occurs half-way through and the rest of the tank-water simply passes through the bowl (rather slowly) out to the exit.
So I guess what I am saying here is that this toilet wants to flush on half a tank of water no matter what. Can that be so?
I have tried shortening the draw chain (to the rubber whatever), and reducing/removing/increasing the size of what looks to be a yellow sponge float on that chain. I have even tried moving that float (if that is what it is).
Am I stuck with this?
Help please
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WAG
The flapper that closes on the tank can get waterlogged or not hold open long enough. Take the top off next time and hold the handle until the flush is complete. If it works fine then you may need an adjustment or a new flapper.
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No No No I said that even when I hold the handle until tank empties its water, the flushing action actually occurs halfway not at the end which is the way I want it. No idea why.
Thanks
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I have found that poor flushing is often due to partial restrictions between the tank and the bowl, generally the small openings under the rim. Good flushing depends on a fast dumping of the tank water into the bowl. Try flushing with a separate bucket of water and you can see what I mean. Pour slowly and you get poor or no siphoning action in the bowl. Dump quickly and it works great. Don Young
wrote:

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If the bowl isn't emptying energetically, then there's a partial blockage downstream.
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Oh boy! You had to tell me that! I'll try to check.
Thanks
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