Needless to say, but thoroughly re-check and re-clean everything that touches your wort (and beer). Then sanitize.I've never had issues like this in the past, the only thing I can't eliminate is the fermenter - it's a stainless steel one but it could be cheap quality? We also got a metallic staining around the krausen ring which I've not had in the past.
Perhaps a valve or port (treads!) wasn't quite clean, then the residue stayed damp and got moldy.
Gaskets/seals are also notorious for growing mold, tight spaces that stay damp.
Cleaners clean, sanitizers sanitize. There's no single treatment that does both in one and the same step.