Just a thought...i had a few semps in a planter with tropical sedums, so I brought the whole thing in to the sunroom for the winter. The semps HATED being indoors and lost quite a few bottom leaves. Is your plant indoors? If so, set it outside. That alone should help with soil issues. That is, unless you live in a rainy place, in which case you need to set it on a porch.
My grandmother grew these inside old boots. She cut the toe out and planted them there!
