According to your position on full charge, I must have three batteries that
are going bad which is not the case.



You do not have batteries going bad because they can be charged to 13.2.

The fact that they then partially discharge to 12.6 doesn't make them bad
batteries.

If your batteries could not be charged above 12.6, they would be starting to
fail.
As you noted, they can be charged to 13.2.