Recovering corals help

[spit.fire]

Every now and then when I'm at the lfs (store sucks and can't keep corals alive) I grab barely alive corals in order to save them

My question is should I be trimming the dead sections of the skeleton in order for it to spread more or will it spread overtop of the old

Here are a few of the corals





And also I've got a bubble that is 80% dead but recovering