Stressed Out Female Gbr, Help!

[xamy_valox]

Hi there, a couple of months ago now I added a replacement male GBR to join my female after her current partner died.
At first they got on like a house on fire, her colours returned and they were never see without each other. Picked a little place and although never actually bred, looked as if they were about to.

However over the last week or so my male has become really aggressive towards the female and won't let her anywhere near him. Goes out of his way to find her and chase her down and generally bully her! She has lost a lot of her coloration and although she is eating and active, you can just tell she isn't happy.

Why would he have suddenly flipped like that? And what should I do to try and rectify it?
I may also post a pic of my male as I'm unsure as to wether he has an abnormal mouth? It looks like there is something white, like a very very small growth just on his bottom lip but inside his mouth. Doesn't seem to affect him and he is eating normally but just want to get it checked. Can't get a pic at the moment though unfortunately.

Any help appreciated as I really don't want to loose my female I'm already gutted as on Monday when I was doing a water change, a Sterbais Cory got too close to my syphon without me realising and I felt him get stuck and then release. Thought he had pulled through ok but just found him dead with a large red mark on his side

 

[xamy_valox]

Anyone?

 

[Brahmza]

I'd assume that at first, the female was happy to be with another male after losing her first, and the male was just excited to be around a female. But after the male settled in, since they weren't initially paired, he became the boss of the tank, more or less. One thing you could do is add in a second female. His bullying may not stop completely, but he would devote at least some of his attention to the second female, giving the first one a break from time to time. I started out the same way, but I had one male and added a female. They had the same start, and then he started bullying her. So I added another male and 3 females. Eventually the two males paired off with a female of their choosing, and took to they're own spots in the tank, and I took the remaining females back to the LFS.