The only way to guess whether they are getting enough nutrients is to see that they have stopped eating the meal. If they clean their plates, we have to add more to the next meals.
With this, though, high fiber is already achieved. It is in all the veggies and leafy greens that are allowed on the prescribed list. Iguanas convert fiber into carbs in their hindgut which has colonies of friendly flora and fauna which digest the fiber and produce carbs. Cows do the same thing with hay.
Read through this article, which is the gold standard for green iguana care.