Why isn't my hammer bright green like in the lfs?

[MoreDakka]

You can see it brown in the bottom leftish area. In the fish store these are bright green. They are under LED lights in the lfs but a single T5 fixture at home. Could the bulb need replacing? Replaced it in January so not even 6 months old yet.

sigh, my tank is bare...I want more...expensive hobby.

Oh and PS - Should i scrape the back wall? I have high nitrates right now (40ppm) and I'm trying to find the culprit as water changes aren't bringing it down much.