It is best to use what works for your particular conditions. If your other plants are doing fine, then these will likely do better in the potting medium your othr plants are in. I use Aussie Gold for my Paphs and they seem to really love it. Other people have problems with it. It can stay too wet if watered too much. For Phals I use New Zealand sphagnum moss, but don't recommend it to others unless they are used to the challenges of using it. In my conditions a medium that tends to hold more moisture works the best. I don't have much luck with bark. So, if bark works for you, then I would use bark. Photos of the plants may help with what the problems might be.