My tarantula's substrate of coconut fiber smells bad after 1 mo. Why? Help!?

The smell is very strong. Is it the the coconut fibers? I try to remove dead crickets when I see them. I did have some bark in the housing, but I remove it after cleaning everything out & replacing it. I am new to this and need some help. Why such a terrible smell after a month? She did moult about a week ago, everything went fine. I did remove the skin. I keep water in the housing plus I spray with water a couple times a week. I do have an undertank heater. Pet store not very helpful.