Hi Kakapo, so nice to meet you.
I have never had good results from using cactus potting mix.
Can you tell me what sempervivum you are growing? Some are tougher in our typical Oregon winter/spring rain and fluctuating temperatures. Many of us here in the PNW grow semps with great success. In fact one of long time hybridizers of semps here in the US lives in Salem, OR. I live in Oregon City, not far from you.
Even in containers, if you have your potting mix correct, you should be able to grow them well.
Can you show us a photo or two so we can see what yours are doing?
