I bought x4 of these plants last week from a local garden centre. I put
1 in a 14inch low pot which is doing ok, and the other 3 in my garden
border.
Out of those 3, 1 has almost died, with no leaves left on it, 1 is
heading the same way, and the leaves are shrivelled, and the last one
seems to be ok for now.

Anyone know what is wrong; is it soil or something else.