I duno why my hamster both of them are fighting.. They both are call Mickey & Mouse.. Mickey is brown and Mouse is white..They both are Winter White hamsters and use to stay in the same cage.. But now Mouse look vry scared and keep on squeaking whenever i put Mickey together.. They keep fighting and bite each other.. I duno is this the reason?

B4 christmas, i was working.. so i cant accompany my gf den i suggest to borrow 1 of my hamster to her for 2days.. Is Mickey.. B4 i pass it to her, i changed new bedding and put lots of water and foods for him these 2days..

My gf den change the bedding again using hers Living Worlds Pine Wood shaving bedding (im using Chipsi Classic).. when she was having it for 2days cause she say vry smelly.. I guess nothing wrong rite?

I observed Mouse this past 2days, he seem vry lonely and nvr moves much.. I guess he misses Mickey..

So yesterday i went back to take Mickey from my gf, den i put together again and they started fighting.. Mickey keep on chasing Mouse and Mouse keep on squeak.. I try changing the bedding and put them together back, end up still the same.. What happen to them? 

Feel so sad right now.. They last time use to be best friends, but now keep fighting with one another.. Anyone can help me with this?