Is this in the 1988 TT? Did you get a newer converter for that TT? If not, then the 6s won't get a proper recharge, which means them seeing 14.4 or better for as long as it takes to get their SGs up to spec, say 1.285 ( after allowance for temperature)
Once SG stops rising that is your target for future recharges (baseline SG) You need to do that with any new battery after getting it home, and especially with these with the extra shelf-time.
Then you should be fine--if you have a converter or some other charger that can meet the charging specs for those 6s.
Yes, it is very annoying to have the RV shop steal your camping time like that.