[fred]

I water my chids in sphag both ways
I mist the top with a pressure sprayer and I also soak the pots to let them soak up some water ( rain water )
if the moss is packed to tight one might have that problem

with re-potting it all depends on your conditions sphagnum moss does not like direct sun light or very high humidity this will cause the sphagnum moss to rot
one can soon tell if the sphagnum moss has gone off it has a sour smell

I would not suggest taking all of your chids out of bark and put them into sphag
I would suggest to learn how to use sphag first.