could someone help me with my itunes card

so a few months hace i bought the single from the wanted lightning with the account from my dad and yesterday i bought there ep also with my dads account the song lightning was also on that ep but because i already had that song it didn't download . Now i wanna buy that ep but the speciale edition with my ITUNES CARD so i wonder because its with the card will the song i have download o wil it just download the songs i don't have if tu can answer it would really help