It's kind of a tough question. Usually we use "des" for the plural, and it will never be false, but "de" is sometime used because it's more pleasing to the hear and maybe more "poetic". I don't know if there is really a rule but I know that you can only use "de" with the plural when there is an adjective beginning with a consonant preceding the noun. Anyway, in this case they are both right.

I'll try ti esplain it to you Generaly we put "S" at the end of the word like : ( table = tables / chaise = chaises ...) But there are some exeption : 1- The words that end by "eu / au / eau" we put "X" except with this word : landau, sarrau, pneu et bleu we put "S" 2- the words that end with "ou" we put "S" in the plurel but with this words we put "X" : bijou, caillou, chou, genou, hibou, joujou, pou. 3- the word that end with "AL" like "journal " we remove the "L" and we put "AUX" like journal = journaux / cheval = chevaux but we have an expetion with bal, carnaval, chacal, festival, récital, régal, cal, serval with this words we put "S" 4- the word that end with "AIL" we put an "S" but with émail, travail, et vitrail. Un corail we evoid the "L" and we write "AUX" travail = travaux "if you have any question ask me"