Get them OUT of the terrarium. CPs do NOT belong in terrariums. Use the fungicide but REMOVE THEM from that terrarium NOW.

I think I should keep them in the terrarium...trust me. I'm in Phoenix and I bet the super-dry climate here will eventually cause the sub-tropical sundews to die from low-humidity. I put the fungicide on yesterday and isolated the possibly infected sundew under a grow light away from the terrarium. It seems to be doing fine. There are even little divisions growing by its crown that are exposed to a wetter area since they're so close to the wet soil surface, that have been growing for about two weeks now. I would've expected them to be attacked by a fungi before the adult plant and that hasn't happened. At this moment I believe that what I saw probably might've just been some super-tiny sand grains from the soil mix sticking to the crown after the sundews' recent transfer to new pots.