Marcus is correct. Match the battery pair capacities as close as you can. Mismatching batteries - for example a new, strong 6TL with an old, tired 6TL - will shorten the life of both batteries. The stronger battery will act as a "sink" and try to pull more charging current than the weak battery can pass, and the weak battery will act like a resistor and limit the charging current. The weak battery will be overcharged, the strong battery will be undercharged, and the life of both will be shorter than if then had been properly paired. However, in your case all your batteries are new, so there should not be a significant difference in the performance of the individual batteries. I would suggest that the "underachievers" you have were not fully charged before testing.
