if you have fill systems on the batteries then overfilling them should not be possible and even if you charge them they shouldnt spill during charging.
You may want to have the battery company that installed the fill systems to come out and check the caps, hoses and connections and make sure they are not leaking. Most fill systems i know of do need to be checked periodically. Floats in the caps can stick not shutting off the flow when filling and can overfill cells. Things such as this may be what you are experiencing.