Nearly impossible to follow this.
"When placing a multi-meter on the individual batteries they each register 7.3v, but if I check ANY combination of batteries in series (2, 4, 6, or all , I get a reading of 11.5 which is about what the CC 'LED bar' meter shows."
I assume this is connected for 12v.
Firstly the only way you will see 7.3v across any cell is if it is fully charged and gassing. If that figure is with panels feeding it may make sense. If not charging or with any form of load then suspect your meter.
" but if I check ANY combination of batteries in series (2, 4, 6, or all , I get a reading of 11.5 which is about what the CC 'LED bar' meter shows."
Now what does that mean? two cells in series are nominal 12v but no other combination makes 12v.
Disconnect these things and leave them stand for a few hours. Connect two in series and ignore the rest. You now have a string of 2 cells and the total voltage must be double that of a single cell ( or perhaps to put it more accurately the 12v reading should be the sum of the 6 volt readings ( should be very close but may not be identical). If this is the case and they have been standing long enough to loose the surface charge then the 12v reading should be something like 12.8v if fully charged ( 6.4v per cell). If you still have the 11.5v then they are flat and each cell should be about 5.75v.
Try a load at 12v such as a car headlamp bulb and see what happens to the volts. If it was at 12.6v or more to start with it should hold up with a small load unless you have unexplained resistance somewhere ( including in the batteries). If it started below 12v then it will fall very quickly on load.
Until you sort what is going on with a simple two battery string there is no point in adding confusion with all the cells. If that pair behave then try the others in pairs and you should start to make sense.
Multimeters have a very high impedance and will measure nearly correct volts even if you have a high contact resistance somewhere but the lamp load will soon show any bad connection. The CFL will just add another layer of confusion at this stage. A filament lamp will glow with only a few volts and let you really see what is happening.
Flux