They appear to be reidi to me due mostly to the size of the snout, the "whiskers" on the snout, the width of the back of the neck, and the coloring. Kuda are generally black or grey, but in seahorses, it is definitely not a deciding factor. The crown also appears to be reidi. The "thorns" are there, but not excessive. It has been my experience that kuda don't have the thorns. They are definitely not erectus.
Whatever they are, your tank is lovely and appears to be a wonderful home for them. Would you please PM me the name of the LFS where you got them?