Seals with multiple paladins

So, it seemed the last time I was tanking, that my Seal of Corruption didn't stack with other paladin's Seals of Corruption. I mean, the stacks shot up faster, but in the end, there were only 5 stacks.
With multipe paladins, should only 1 be using Seal of Corruption? What seal would be best for the OT's or Ret pallies? (still Blood for Ret?)
_________________
Suzumiya: 70 prot, Eldre'Thalas, Belf

I have not seen that issue with two palains tanking. SoB/M is the best off tank seal if mana is any issue, otherwise use SoV.
_________________
Majiben

As far as i know multiple SoV does stack (meaning, they put different DoTs on the mob), like warlock / Sp dots.

You probably were confused by something else.
_________________

R.I.P. Sanctity Aura, it's Hammer Time