If the humidity stays high there may be to much moisture in the substrate, A good rule of thumb when it comes to expanding substrate and keeping it moist is when you grab it in your hand you want it to clump into a nice ball when you squeeze it but not have tons of water come dripping out of it. To much water with all that heat becomes a breeding ground for bacteria. Also are you using something to declorinate the water for his dish and expanding the substrate?