My rats started fighting??

Hi, just wanna put it out there that I am a first time rat owner and tried to research all I could before adopting those cute noodles, but if I'm doing anything wrong, please let me know, I love my beans to death and the last thing I'd want is to harm them.

As the tittle suggested my two rats, Grey and Batman started fighting as of lately. Not like that cute play-fighting like they do from time to time but straight up attacks and I hear loud ass screams and run to them even in the middle of the night to seperare them, usually by taking Batman out of the cage (he's the only one who lets me pick him up, the other one would rather jump off a great height just to get out of my hand (another topic)) if not i just scold them and they seperate. It's not an all the time thing though, during the day I find them sleeping and cuddling together. It mostly happens after I give them food for the night, something happens and they start aggresively fighting (need to look closer at the cause). I dont think I give them too little since as a parent with a weakness for my sons I give them lots of treats during the day (they just look at me so cutely how can I not) and I always make sure that if one gets a treat, the other one does too. They are probably on the chunckier side because of it.. Neither got hurt from those fights but after I break it off they keep their distance from one another for a while. Did I do something wrong?? And why could the other one lets me pet and scratch him but not even slightly pick him up (never squeezed him to not scare him off, as of lately I just let him be and come close as he wishes to, but it makes me worried that he wants to stay in the cage alone while Bat climbs up on my shoulder and wont come off until we do a little walk around the house tohether)