Brew,
Without the ability to look at your batteries it's hard to say, but here's my suggestion.
Buy a hydrometer. You know, the thing with floating balls that measure the specific gravity of the acid in the battery. Test each cell when you think you have them equalized. They should test out to have 13.8 volts per battery or 2.3 volts per cell after resting for an hour or so post equalization (or better). There should be very little variance in this hydrometer reading between cells in a new battery. Just because they're new doesn't mean they are good.
You state that these are full of distilled water. That's what one replaces low electrolyte, which is not with what they should be filled. The hydrometer will tell you exactly how concentrated the acid is. Also there is a point where adding more water than needed dilutes the acid too much. If this is the case careful extended equlaization can correct the problem by evaporating some of that water and bringing the specific gravity higher.
If in doubt have Wally World replace them under warranty.
How are you equlaizing these now? Is it a grid tied charger and if so by what method are you checking the state of charge? A simple Wally World digital voltage meter should get you close enough when combined with the hydrometer readings. Is that what you have? To truely equalize one needs to hold the voltage on a 12V system at 16V with about 2 amps of current for around 2 hours. During this time be careful not to allow the batteries to get hot. They will boil, and that's the point, but the low current will not damage them, it will just drive off the sulphate from the plates and mix the acid. This is not a result of heat. Be sure to keep an eye on the acid level and NEVER let them get the paltes dry. Most off the shelf automotive chargers will not do a good job of equalizing.
I don't think you have a 4 watt inverter. I assume you meant 400 watt. Depending on the type of inverter this 400 watts, if run at full load, will be 33.33... amps drain on the 12V batteries. So 230 AH batteries, if really healthy, will run the 400 watt inverter at fulll load for about 7 hours before going to the dead point 100% discharged or aprox 10.5V. Assuming 100% efficent inverter which none are. I would bet a healthy battery in this amp rating range should supply that inverters full load for more like 4 hours. Your inverter may have a high cutoff point for the battery voltage, test that too.
I also feel your range of useful voltage is way too narrow. The difference between 12.72V and 12.46V is only .26V. I typically range my bank of 12V batteries from 14V to 11.75V, a difference of 2.25V. I have taken them much lower, but try not to do so, especially this type of battery as they are not true deep cycle batteries.
So provide us with some updated info and we'll be happy to try to help.