Welcome to BGW,
Here is a diagram how you should be wired. All 6 batteries should be wired together in series as shown below.
Run a longer wire to the "Main -" of the 6th battery to connect all 6 batteries of your pack to your charger. As connected now, you are only charging the first 4 batteries.
The charging wires should be connected to the "Main +" and to the "Main -" (battery 1 and battery 6). Make sure your higher amperage cables are in direct contact with the lead base of the battery terminal terminal studs and the lower amperage charging cables are above the high amp cables. This will reduce resistance in the connection and avoid heat buildup. Also note the torque on the Trojan stud connections is
95 - 105 INCH Pounds ... which is only
8 to 8.8 Ft - Pounds ... not very much torque. Over torqueing these connections can result in the studs loosening from the lead posts, which results to an increase in resistance, leading to increased heat which can result in melted battery posts ... it happens often if post connections are over torqued so use care.
Also find attached a state of charge chart for your reference which you can use to convert your battery voltages to a State of Charge percentage. You can see that those batteries at 6.03 volts are only at a 50% state of charge.
