were installed yesterday afternoon and are still showing as good this morning
I'd suggest that you get some type of battery monitoring that is accurate and easily visible. This could be as simple as a voltage meter. The factory built idiot lights are not accurate.
Your new 6V batteries are going to actually increase in capacity over the first 10 or so discharge/charge cycles. A hydrometer will measure, exactly, a full charge and offer a baseline for future charging.
Without an accurate monitor, you will be repeating the battery replacement process sooner than you'd like.