When you add the rock, it may introduce some more ammonia into your system. So you may want to put it ina rubbermaid container with a heater and powerhead for a few days. Most people, including me, experinced a very minimal cycle from adding rock to a tank. Or you may want to add the rock to your tank and QT
the clowns until they are healthier.
Try adding some garlic extreme to the food. Sometimes this will help a fish that has stopped eating.
Also, think about a cleanup crew. BTW
, what kind of water are you using? Tap, RO