Yea it's seem he is lacking that tag. He has 2 chakra elements so he should has kekkei genkai.

A lot of people in Hidden Cloud has blood limit. Darui do has blood limit called Ranton which fused Lightning and Water chakra, not to mention Darui is the only ninja alive who c*e Black Lightning.
Same case for Mei (Futton) which combined Water and Fire, Hashirama (Mokuton) which combined Water and Earth or Onoki (Jinton) which combined Fire, Wind and Earth.

You're right. The fact he has 3, 4 mouths on his body he should be treat as blood limit or at least secret jutsu user.