I have a Tappan stove. We live in the country, so it runs on propane. Starting two weeks ago, the flames on the cooktop started to burn not as high. It started in the back left burner, then front left burner. Now the right back burner is burning low (the flame is about half the height as it used to be when turned to high).
Is there something wrong with the stove, or could be a problem with the regulator on the propane tank?
(not sure if that is the correct range model -- the one on my paperwork says 30-3991, but I wasn't allowed to use it.

Kitchen Ranges - Tappan - TGF320 Gas Kitchen Range