Ah what kind of soil is that?
I think that as long as the pH of your soil is good once you start feeding normally you're going to see better growth; also, more light IS important as a leaf that gets no light WILL eventually be sloughed off by the plant as useless.
If you cant find fish fert, get blood meal and scratch a little into the surface of the soil according to the package directions, or just look for a DIFFERENT complete fertilizer that has a high 1st number, and MICRONUTRIETNS!!!