The first voltages you mentioned .... 28v abs, 26.4v float, 29.4v equalize.
sound pretty much the norm to me for standard flooded deep cycle batteries
29v Abs, 27v float, and 31v equalize
seems a bit extreme ....that's more than what most AGM manufacturers recommend for batteries that have a higher acceptance rate than yours.
Are you sure your battery monitor is reading / setup correctly for these batteries? As Mark said..Peukert constant set correctly?
My understanding is that lead acid batteries only need to be "equalised" in the case of sulphation caused by repeated deep discharges followed by incomplete charging.
It sounds like you are charging your batteries fully and limiting discharge, you shouldn't have a problem....maybe it's the meter that has the problem..?
Opua, New Zealand...for now