The Sims 3 Putrid Omni Plant?

I've got the omni plant, and figured out what it does. I fed it with death fish, Life plant etc. but even tough I feed it with outstanding death fish and used outstanding vegetables to fertilize it, why does my omni plants be horrifying or putrid? Am I doing something wrong? All of my other plants manage to be outstanding, but what is wrong with the omni plant?