I got my baby the biggest size diapers and pullups but she keeps having a mark thats purple on each…

I got my baby the biggest size diapers and pullups but she keeps having a mark thats purple on each side of her hip where the diapers close what can i do its been months thats is not going away:(? Im waiting for underwear that i ordered special with inserts and a potty im so sad its just not going away!