Dave;

Probably the cheapest thing to do is re-evaluate your loads and see if you actually need that much battery bank. It's easier to take some out than to add more in. Then evaluate the batteries themselves. Charge them individually if necessary and see which ones come up and stay up the best. Use them and disregard the rest. You'd be amazed at what you could run from 210 Amp hours @ 24 Volts, which is a lot easier to wire up evenly. See the Smart Gauge wiring diagrams: http://www.smartgauge.co.uk/batt_con.html

Never use method #1. Number two is good for one parallel set and for what you've got now (six in parallel) only method #3 would stand a chance of working. At best your existing array would support three parallel sets of these batteries (315 Amp hours).

And yes, sometimes dropping batteries makes the whole system start working much better. Seems counter-intuitive, and yet it often works.