My Whirlpool window a/c is not cooling as well as it did last sum

mer. It does blow refrigerated air (just doesn't feel like its cold enough), compressor comes on, etc. I set the "temp" to 64 (lowest) put it on "low fan", "power save". It cycles like it's supposed to, then the temp gauge for the room temp goes to 64 or sometimes even lower (I know it is not 64 degrees or lower in my house) and the compressor goes off. If I put it on "high fan" and "cool" it seems to bypass the temp setting but it still doesn't seem to get cold enough. Any ideas? Coolant leak? Thermostat problem? This is only it's second summer.