are you hydro or soil? there are 3 part ferts that you can use, for example, the botonicare has a 3 part called Triflex, this has a base, grow, and bloom.... then you can add others to it like sweet, calmag plus, etc..... The best advice is to go to a local hydro store or something and tell them you are growing indoor "tomato" plants and they will help you with what you need.