Kathi I have a couple Dendrobium's and a Epicattleya in lava rock and they are doing quite well in it. I do believe you need to water a bit more with lava rock as the medium versus bark mix's. It could be that your right about the rock drying out to fast. As you know Cattleya's like to dry out between waterings, but they may very well want to continue to 'sip' in between time. If it were me and its been a long time since you have seen new growth, I would repot in medium size bark, perlite, etc. I admit to know nothing about stalite and am hoping someone else can help you there. Good growing! AL