Be careful about reusing soils, bags, perlite, etc.
There are various fungi/bacteria associated with problems like damping off, etc. and when you start a new grow in old pots/equipment, these germies will regrow in the new set up and give you the same problems.
Perhaps start with new perlite or at least put the old stuff in the oven and bake at a high enough temp. for long enough to kill off any bad bacteria - it will also kill off the good bacteria. I know people would do this to soils... apparently the smell is bad so if your other half is precious about the oven...
j