Some blocks i destroyed in layer 1 of the ender always reappears after i quit and come back in my world

I put some blocks in layer 1 of the ender world, then destroyed its. But each time i reconnect to my world, they reappears, et i can destroy it again it will be the same the next connection. Is something possible to be done ?

Thank you for your help, and i'm french i hope my english is not too bad