Cant hit Illaoi tentacles with deadly plumage up.

was playing a game with xayah and i had deadly plumage still up so i continued to go clear illaoi's tenicles but i couldnt, non of my autos would deal damage to the tentacles. my feathers was hitting the tentacles and going though and landing in the ground. hit was a 1hit tenticle and i hit it 5 times XD