According to their website, those toilets use a Fluidmaster 400 fill valve. This is a good fill valve but it sounds like yours may have a little trash in it. It's not too hard to pop the cap off the top and take it apart to clean it. You can also replace it very easily. Fluidmasters are available at almost any hardware or DIY store.
If you make sure and buy the same kind of Fluidmaster there is a trick that will make this fastest toilet repair you've ever seen. First, turn the water off to the toilet. About half way down the fill valve there is a retaining ring that snaps down to hold the valve together. You can see this very easily on a new one. Just pop the ring up and pull the top half of the valve off. The valve body is threaded to allow for height adjustment and you will hear some clicks as the valve comes apart, that's OK. Do the same thing with the new one, install the new top on the old bottom, pushing it down far enough to make sure the top of the fill valve will be below the tank lid, and snap the ring back down. Make sure the ring is down all the way and secure. If it's not it will look like an episode of the Lucy show when you turn the water back on and you will get wet. Turn the water back on and adjust the water level with the little clip on the side. If you do this right it will take longer to open the box than to replace the Fluidmaster.
Check out my goofy video for my new
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