Thanks; so you think that the browner color comes from more light, rather than less?
From what I have read, generally yes. These Bronze plants are supposed to have different colors going on. Mostly what I see online once full grown is a more green leaf with the bronze colored stem. But I have also seen them in more high tech tanks with mostly bronze leaves/stems. I also know that with the pink and the red Crypts that those are reported to have more color the more high tech you go.
These Bronze Crypts, I have seen them sold in different color schemes, like mostly green leaves with the bronze stem, full bronze, mostly green with hints of bronze. I originally figured these were different strands of the same species of Crypt. I know believe it is due to the lights and nutrients, for the bronze as well as the others (pink and red Crypts) that I have read about.
Backing up a little with my Bronze guys. These are tiny and really I feel I need to mention that. But the new growth is obviously a more brownish red color than the original green leaves. The stems are also more red than than the original stems. My tank does have injected CO2 but nothing crazy, it's just a diffuser and I add as much as I can without bubble build up on the top. I am not doing the 1.0 PH drop or anything... And I am running a single 48" Fluval 3.0 that has been tuned down over a few weeks to dial in algae issues. for nutrients I have only been doing root tabs with the occasionally addition of Iron. though I misplaced this or my baby moved it.... so that hasn't happened since I got these Bronze Crypts. So just root tabs. I see that I got Potassium in the mail today, there are holes in many plant leaves, going to try this out.