First Organic Indoor Grow- Fungi

I have made the transition to my first supersoil grow and my plants have been responding nicely. A few weeks ago I prepared a top dress to be used into the first few weeks of flowering which consisted of worm castings, bokashi , kelp meal, bat guano, bone meal, glacial rock dust, and kelp meal. I mixed it up in a pail with a sealed lid and put it aside until plans to use next week. When I recently opened it a fungus growth has covered the entire surface of the mix. A grow pal indicated that this was good sign of microbial activity and suggested to stir it up and used as planned. Any feedback would be appreciated.

Cali OG Kush

Cali OG Kush

Here are my plants and day 11 of flowering

was it stored somewhere cold? or was it warm? USually you need warm temps to have bacteria growing so he might be right on the beneficial fungi..

Stored in dark area at temps about the same as my grow which is averaging 77 F