I have purchased some advanced echeverias and planted them in a prepared garden bed. However they have nearly all developed 'black spot' on the leaves. I don't know what the 'black spot' is, but if left the leaf will quickly rot away. The most affected plants are the 'frills' with the large fleshly leaves.

I have resorted to removing the affected leaves, in the attempt to keep the rest of the plant free from the 'black spot'.

The soil is made from 20% coarse sand, 70% sand/soil and 10% potting mix.

The plants are east facing so they recieve 5 hours of direct morning sunlight.

The plants seem to like the condition as they are developing
pups and lots of new growth.

I don't know what is wrong. Is it the soil, the rain, an bug perhaps? Any help is most appreciated.

thanks

-lp