There are a number of low light/low tech plants that you could add. Crypts, java ferns, anubias, swords, ludwigia, hygrophilia, to name a few. Are there any fish? You will have to add macros at some point since Flourish Comp is mostly micros.
Also look into dry fertilizers, as all the liquid ferts are mostly water. There are several vendors online and I know of one member, nilocg, that sells on this forum.