What's wrong with my beets plz help

[Bleys]

 

[Anniekay]

From what I can see, it resembles leaf miner damage. I would suggest that you remove and dispose of the damaged leaves, then spray both sides of the leaves with neem oil.

 

[Ruderunner]

Agree, looks like bug damage. The advice above is good.

Don't worry about removing too many leaves, they'll grow back.

Also, mounding more soil on top is beneficial to growing larger beets and keeping sunlight off the roots prevents them from developing a though skin.