Place a clump of damp moss in each hide.
https://www.amazon.com/Zoo-Med-Terra...s=zoo+med+moss
Keep it damp during a shed and allow it to dry out between wetting during non shed periods. Its cheap and easy and works like a charm.
Since the snake stays in the hide the majority of the time the damp moss gives the snake a constant humidity boost right where it needs it.
If you soak again the water should not come up higher than 3/4 of the snake's side.