Air Circulation Question

Moist air is heavier, and that's a tall, narrow box of humid air. You need to get some fans to help move the dry air down and moist air up. It sounds like you have enough gear to get the RH right, just move some air!

I just watched a video on your Hydra (since I'm not familiar with it); just add the extra fan kit, and have it blow from the top down (assuming you have the hydra on the bottom). Make sure it has an unobstructed air path if possible.