What has happened to my betta?!

[Jacobwt]

Any idea what this is? He does look a little bloated but shouldn't be displaying this behaviour. And why has his face turned purple? If anyone knows what's wrong here I would like to know, thank you very much!

 

[54seaweed]

water parameters would help , but with out them I would suspect ammonia poisoning

 

[Jacobwt]

I also have a female betta in the tank and 2 Amano shrimp, no signs of illness, water peramiters are 0 ammonia 0 nitrite 05 Nitrate, my other male fighter has just died a sudden death when I got back from work, I have 2 12 litre tanks set up side by side. Each tank has a female betta as well as 2 Amano shrimp. (Female fighters are in breeder boxes)