Watering System overwatering

[n8xwb]

I have a 2018 Precedent with a watering system for the batteries. For two years it worked great....put the syphon in distilled water bottle, attach to battery connection and pump the rubber bulb til it gets hard. I never had any issues, or water boiling over out the battery vents. Now, when I use it my batteries are always overflowing. I opened them and all were overfilled instead of having ½" of water over the top of the plates.

What causes this? How can I fix it?
Must I buy a new system?

Thanks!!!!