Bleach is not great for the flutes since it will be in contact with the mouth. That’s why I do a fire treatment, the heat is enough to boil the oil and moisture inside the bamboo. You can see it bubbling and steaming on each end of the flute. That should be enough to kill the mold in conjunction with the oil.

I have two dehumidifiers but they are in the basements. Might need a small one for that flute room.