I grow a lot indoors, being I forget to check stuff if it's outside.
I have some Lion's mane growing a humidity controlled tent, but I'm getting a lot of feathery Lion's mane fruiting, without the substantial fruiting body. Doesn't this sound like the CO2 is too high? This is much too much fruiting mass to be a contaminating fungus.
Sounds like you need more air exchange for starters, and yes it is probably too much CO2.
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