What's your pasteurization method? Longer is better--3+ hours is what I do.
Plus, everything Mikey said is spot-on, of course.
I steam pasteurize between 145 to 165 but I've been doing 2 hours, so noted that I need to extend this out.
I would look more into the substrate you're using and also balancing the PH for optimal growing conditions for what you are trying to grow. Watch your temps too. Anything thing you can do to give the friendly mycelium the upper hand and give the trich less favorable conditions. Start with testing the PH and seeing where you're at to begin with. Your sub should be slightly above 7 to start with in the beginning. You can start a little higher too and over time the sub becomes more acidic then eventually succumbs to trich anyway. When working with tub and especially if you're working with a lot of them, one can only work as clean as possible and you will never be 100% clean, no matter how many times you bleach the walls. One can more easily dial the environment favorable for our friends than can clean a room while still being able to inhabit such area.
Very much wisdom in this post. One skill I have not been working on is measuring PH. It just struck me as odd that the tubs looked fantastic from the beginning, fast mycelial growth, my popcorn grain spread to the substrate and took over evenly, condensation on the walls of the tub looked even (not dried out like my previous tubs), and then after exactly 3 weeks of beautiful growth and 100% colonization, then and only then do I see any green on the top of the tubs. To be fair when I pitched the tubs in compost, I did notice one of the six tubs had mold on the bottom of the tub as well, which reaffirmed my overly cautious stance of not trying to salvage the tubs by spot-treating the mold spots. Thanks for the advice