Then only Acro I currently have that should have yellow is a RR Wolverine. I've had it since about May of this year and after about a month or so, the yellow corallites faded. Last week I started dosing nitrate via a potassium nitrate solution. My nitrate is now up to around 5ppm and the wolverine has it's yellow corallites coming back really strong. I'll try to get a picture.