Yes...having animals in the same rack can affect him. His nose straight up may be a sign that there's one he wants. Although this can also be a sign of an RI. Check him out carefully.
At this time of year it's almost a given that a 450 gram animal(especially male) will go off feed. If the person you bought it from was breeding it, there's even more of a chance(99%). This is not a very large animal, so you do need to worry a leeetle more than older larger animals. If it appears to be losing weight, you may need to get some food down it's throat with force feeding. BG knows this seems kinda drastic, but males will just let themselves die during breeding season if they don't eat.
A small dose of Flagyl usually fixes this prolem for Big Gunns, but not always. BG has a couple males that he may need to do something with shortly. He's keeping a close eye on them and removed them from breeding.
Also, you need to contact the seller and ask exactly how it was set up and what EXACTLY it was fed. Your pics show that the substrate is some kind of paper. If your snake was kept on Aspen, they usually will go off feed if put on paper....of any kind. Contact the seller asap and ask all the pertinent questions.