Some buns have damaged nasal mucosa, sometimes from an untreated URI way back in the past. A URI without overt signs like excessive sneezing or thick snot can easily go undetected. I had a bun like that, he was 6 when I got him and he had some health issues. Antibiotics didn’t help his nose, but he had no thick, opaque or colored nasal discharge, so my (very good) vet didnt think he he actually had a bacterial infection, just chronic thickening of the mucosa in the nose and nose area.
Whatever it was, it didnt seem to bother him much tbh. He had lots of energy and good physical stamina. If he’d been a human he could’ve been prescribed nasal spray with corticosteroids to reduce swelling, but cortison is unfortunately not a good option for rabbits. And even for a human, chronic use of steroids can do more harm than good in the long run.
If the homeopet drops are rabbit safe and seem to help him, I think they could be a good choice. Just look into how long you can give them for, maybe make pauses now and then, obv don’t overdose.