I have no idea how long a fungus can go from spore to fruiting but many of these are similar to the ones I saw in the pile as it progressed, and the few articles I looked at suggested a month, which would match well the timeline of six weeks since application. It also helps that we have had much more rain than normal. I know that there were plenty of spores in the piles; I would use rinse water from empty fish oil totes and pour it on the piles a couple times per year. In three days I’d have a “white icing” on top. It also possible though that the rain and fish oil application has got the local fungi working. Wait and see, but it’s fun to be sure.