Hi. Does anyone have any advice on how to handle the smart but not exceptionally-gifted siblings jealousy?

It is very important to me that I take care of all of my children's emotional & educational needs. I am very proud of them. But they still see things as a competition they are failing. The second one was labeled gifted the others began saying "I am stupid" and that is not true.

Any ideas on how to help children see that normal is not a bad thing?