I eventually finished drenching right through my mesemb collection, it took 5 large bottles of chemical and a lot of moving pots to pour chemical through and re using run off. Now I just have to wait and see. Hopefully I will see and improvement when I come to start repotting next spring.
My only problem seems to be that some of the plants have drawn up a lot of water, and I am seeing a few split sides, and some have decided it is time to start shedding skins and dividing, with new heads visible from beneath. I'm sure it is totally out of season for them to do that. Most though seems fine.