Having troubles…

My last 4 tubs now refuse to colonize my substrate once I introduce the colonized grains. I’ll get a few little knots here and there but it refuses to fully colonize. Now I did get 2 of the tubs to colonize eventually. But now they won’t fruit. Introduced FC about 3 weeks ago and still nothing except an abundance of mycelium. Any tips, teks, or tricks you guys got for me? I could really use it.