I see some autumn-like colors at top... maybe dark leaf underneath?
I have one currently that does that - purple leaves / red leaves. If cold at night (or day) maintaining a bit warmer climate can reduce it... i wouldn't worry unless it dominates and spreads quickly.
in a 30"x40" canopy, i probably have 2-3 patches where some of that exists, roughly what you have, but in winter if i don't keep temps up at night, it can look like Fall in my bloom box.