The rocks in the hymidity trays are a definite must! Otherwise your plants are sitting in water and that WILL kill them. There are humidity trays available for sale that have plastic grids on them so you don't need rock, but they aren't cheap. I live in So Cal, but reasonably close to the ocean, our humidity is about 60. But I still use humidity trays and mist in the morning becuase the AC does dry out the air. As does the heater in winter. You may want to check to see if your plants are either too wet or too dry, I believe recommends sticking a toothpick or cu-tip swab into the pot to see how wet the medium is down a couple inches. I will admit I just stick my finger down in to check... not terribly sanitary, but I do rinse and dry my finger between plants to avoid spreading disease..