I've been using Amgrow Pot & Peat and all my plants have gone into it -
herbs, hibbertia, potato vine, frangipanis & cycad. I'll have to check the
ph of the soil and see if there are some plants which need a change.

The fungus was in a terracotta pot which had an old oregano plant in it and
I also found a fair bit of it in the large pot of hibbertia.

I had two pots of hibbertia using the same potting mix. The plant in full
sun flowered continually, it's roots didn't grow much this summer and it's
leaves filled out only slightly and it had the white fungus. The other
hibbertia which had no fungus was in a slightly cooler position, still very
sunny though, it never flowered, but it built up an impressive root system
and filled out it's leaves and even grew a few new stems.

The fungus in the oregano pot was all around the inner surface of the pot
and mainly over the outside of the compacted rootball, it didn't appear to
be living on anything in particular. The hibbertia fungus was in the soil
and yes, it stuck mainly to bits of cut root and bark.