Hi,
Your connection arrangement is not ideal for your situation, you haven't said what gauge wire you are using to interconnect the batteries but your daisy chain will not help the situation.
You have to realise you have current to charge your batteries, not voltage, so making sure the current flows somewhat evenly is essential with a system like yours that is capable of 50A charging to a large battery bank.
If in your setup you had 0.2V drop from battery to battery, 5 links = 1V difference between the one connected to the PV/load end and the battery furthest away, when charging or discharging that will have an effect.
This is arrangement will give a more even current distribution.
Have you measured the voltage difference across your links when high current is flowing.
When did you last service/clean your terminals/wiring?
Tom... 