Odd discoloration?

Over-all, I think my plants are doing well, but today, I noticed a very peculiar discoloration, it doesn't appear "unhealthy", but the pigment goes straight down the middle exact seems more like an odd birthmark, than a deficiency?

Looks like genetics, nothing is wrong

I'd keep an eye on her. Two different leaves, two different tops...your plant is trying to tell you something. Don't fret, but don't sweep it under the rug. Good luck.