I have a question. What would make a yellow leather turn gold/brown? I bought one about 2 months ago. I acclimated it slowly to the 400 watt bulb it now sit under. It starter at the bottom of the tank and raised it 6" every week. It now sits about 14" directly under a 400 watt Iwasaki 6500K bulb. It looks very healthy and has great polyp extension. All water params are normal. It started out a nice yellow and is slowly changing to a golden brown.Any ideas? Bob