I guess I posted too fast without doing my research.. What I thought were females are, from what I read, males. I hope this dose not turn into a problem with aggression, so far I've had none.
I used to own quite a few kenyis. The reason why "she" turned yellow is because its actually a male. I know, you probably were told it was a female but she was probably hiding her sex to avoid confrontation. The yellow means that they are sexually mature. I had a female develop an egg spot but I vented it and it was a female. She died though.