I second Yote's opinion, definitely DO NOT add any more animals, ESPECIALLY inverts such as crabs or snails, while your ammonia and nitrite still read anything but 0. Inverts are extremely sensitive to water parameters (more so than fish), and ammonia and nitrite will quickly and easily kill them.
I also think a 12 gallon is too small to mix a damsel and a clown.
Be patient. Don't add anything more until your cycle is done (ammonia and nitrite at 0).