fertz can't hurt... unless you over do it. If you want to spend the money on it I say go for it.
I can't say first hand how good or bad they are. I upgraded my lights the same time I bought and added some SeaChem fert. My plants have taken off and are growing like weeds. But with adding the extra light I am not sure if it is the light or the fert or both.
My plants are java ferns and anubuias so they are also low light plants. I am just trying to apply what little I know.
To me I look at the fert as like adding a healthy meal or vitamins to a diet. The fish waste seem to be good enough for the "low care" plants, but adding a vitamin always helps