If it won't eat anymore pokeblocks and doesn't evolve, that means you'll have to get another one. Blue and indigo pokeblocks aren't the best things to feed it, 'cause their level thingy (I forgot what it is called) isn't that high. (Only like 10 or something) I would reccomend using different berries such as kelpsey berries, when the berry master dude is in the contest house. (Though i think he only appears on emerald.) If you don't have emerald, just use berries that don't do anything (Ones that have the description saying "Plant in loamy soil to grow *Insert name here*")
they usually make better pokeblocks than ones like chesto berries and the like.
Oh yeah, make sure you only give feebas pokeblocks that are dry because dry raises the beauty stat.