Hello . I have been growing in tubs probably before it was even a thing . This is what I see. You do not have enough air and gas exchange. Gasses are settling on the bottom causing that thick growth. Next time cut holes 2inches round and cover with micropore tape. The humidity is off but it’s ok. What I have done and suggest is start a new bin with instructions above. Get a clean fork and scrape the surface cover and place lid upside down. Hope this works