en_tn/lev/13/55.md

after the mildewed item was washed

This can be translated in active form. AT: "after they washed the mildewed item" (See: rc://en/ta/man/translate/figs-activepassive)

it is unclean

Something that God has declared to be unfit for people to touch is spoken of as if it were physically unclean. (See: rc://en/ta/man/translate/figs-metaphor)

You must burn the item

Here "you" does not refer to the priest specifically. It just means someone must burn the object.