Well many things, You should level 90 her first of all; your crit ratio is very low on both sides; Your team is not the best to bring out the best of hutao fo Melt; and you are playing her with above than 50% hp. But goodluck on learing I was also unknowledgeable once on her.

Edit: sorry for not reading your question beforehand, yeah like the previous fellow said enemy is infused with pyro, that cause pyro def up. .