Oooh that's a bit drastic?
I'm not a cacti/succulent person -- I have a couple (well, OK -- a quick mental inventory is telling me more like a "few"
) , but mostly succulent/euphorbia type .... So my experience is limited.
That said, I think its generally easier to take care of plants when they are individually potted, especially when there are variations in their needs. You can also apply more severe treatments to affected plants without involving healthy ones.
If the soil mix look inappropriate -- and mine tends to be a lot sandier and with something gravelly -- pumice gravel, calcined clay, perlite as last choice -- I think that would be the first place to start.