New to fish keeping

[ABCatie]

I currently keep 3 fancy guppies in a 3 gallon tank. I have to filter or heater, and I change out 2/3 of the water everyday.

Is this water changing schedule too frequent?

 

[ABCatie]

Also, all 3 of my guppies are male, and one of then is constantly bullied (a chunk of his tail is missing), does this go away, or so I have to change out 2 of the males for females?