Im no expert in mycology but most of what ive read leads me to believe that a body of water is a contam risk, what is your fruiting temp[oops see you told me already]? should be just under colonization temp (temp drop to initiate pinning) as higher temps will encourage contams

You giving it light?

Filters in fresh air, does it filter out CO2?

If you wanted something more simple to maintain I think a monotub would have been better and larger yielding

Cakes and SGFC i think are the right combo to use

Altho maybe its something else, hard to tell as I dont know your procedure exactly