Ken,

It's possible your problem is quarry sap, if the stone is new.  On the other
hand, the mason foreman working on the NYAC told me the other day that ya
gotta be real careful setting/pointing LS. Ya set it in (regular) mortar and
point it with a very dry mix, otherwise you get discoloration of the mortar
at the edge of the joint (I don't remember that it was orange though, or that
quarry sap was orange either); the mason claims the LS "drinks" water.

Coolest personal regards from the NJ office,

Ralph