Hi,
What the results indicate is chronic under charging of the battery bank.
How often have you depleted them to "dead"?
How many watts of solar are there?
What is the ambient temperature this time of year?
Optima batteries are not often used for deep cycle storage. Why? Because of the spiral design there is a lot of "empty space" that a more tradition grid and paste design fills with lead. That means the Optima per unit of volume used (not the actual cells but the foot print) is considerably lower.
At this point, what may be needed is reconditioning or equalization of the batteries. That is much more difficult with the AGM format, so I'd be writing to Optima to ask for their specific advice. I'd also do one battery at a time.
If you don't wish to take the "risk" of equalization, at least find out what Optima recommends for a maximum charge voltage and tweek the existing equipment to provide that during charging.
Another strategy would be to spend 168 hours on shore power to see if that will return the lost capacity. Do the research necessary to find out the best voltage for doing that.
With such a small amp-hour capacity battery bank, I'd recommend leaning towards 150 watts per 100 amp-hours of capacity. I think the Blue tops are about 85 amp-hours each, so the solar system needs to be approximately 400 watts. The bare minimum would be approximately 160 watts.
