your thoughts please

i have two plants that are 5 weeks old, im running out of space height wise, my question is, a 28 x 28 inch x 6 foot tall closet be enough space for two plants?

Height wise it should be fine, start topping them if you haven't been. When their around 2ft in height start flowering them or slowly bending the stems over, or under a cage.

Are you flowering already?

might be a little cramped depending on how long you veg them but hight should be fine as long as you don't wait till they are two feet tall already before flowering them. mine went from about 10in tall to about 24in during flowering, so you be the judge.