IME Vals often melt when they are transplanted and others have the same experience. Not sure where they came from in your case but if they were in soil, for example, and you planted them in a gravel type substrate I'd expect them to lose most of their older leaves. Once they get settled in they should throw out new growth. They are not very demanding in terms of light, co2 or fert and will reward you with a lot of growth if they are happy. A leaf will not grow if placed in the substrate. Root tissue is needed. Or a really good spell.