I partially agree that a strong ammonia smell means they're not clean enough, but my DD went through a phase where her overnight sposie smelled pretty strongly of ammonia. She slept for 14 hours at a time and just had crazy caustic pee. But I definitely agree that rinsing it out in the morning is worth a try to see if it helps. And using a little bleach.
Rebecca, married to J (2007), DD1 Anna (11/09) and DD2 Ada born at home 7/12 DS Henry born at home 3/14