Kept forgetting to buy distilled water, finally did so today, my 2nd battery bank was in need of maintenance. Good thing I didn't wait any longer, some of the internal bus bars were exposed. Thankfully the plates were ok.
Now I switched the charger to just that battery bank for a bit, then I'll turn up the other bank. I should probably set myself a reminder to do this like every 6 months or something. I tend to do it just whenever, no schedule.