Are there any anatomical differences between Blue, Fin, and Sei Whales?

[EpicRaptorMan]

Aside from size of course. They are all rorquals afterall.

I recently purchased the Sei Whale from Safari Ltd and I am rather disappointed in the sizing. It's extraordinarily small compared to my other whales in the collection, but the paint and sculpt are great.
I was wondering if, with slight modifications, if I could get a Blue Whale from another brand and have it pass as a Sei or Fin whale to stick true to my 1 species clause. I believe there might be some slight differences with head shape between the three and obviously size.