I'm aware neutering does nothing for their dominance stuff, but I intend to work as a vet, and currently work in the grooming salon of a petco, so I don't want to accidentally bring home sow-smell and have it agitate them (or any other similar smells, to be frank)
Honestly the only one that fights is Ren. The others accept Ren and Qrow as dominant and never quibble... At this point it may just be easiest to rehome Ren...
There is no excessive scratching that might indicate mites, I'm fairly certain there's just been a lot of nipping. Especially as there are no other bald spots (this one is roughly 2 cm across and almost perfectly round, just off to the right of his spine) and there are many small lumps under the fur from what I can only assume are shallow bites.
Please be aware that neutered boars still react to sow scent. I've currently got six myself, so I should know! Washing your hands thoroughly and changing your clothes when you come home is much more effective.
I would still consider mange mites or fungal - the discomfort/pain in the skin can lead to self-mutilation. Those little bumps you can feel in the skin could well be mange mite eggs. Mange mites are not always characterised by scratching. The concentration in one spot argues strongly for that. If it was bites by other boars, you'd usually find them all over the rump.
If you want to become a decent vet, the first thing is always to very carefully close out any medical angle and not just dismiss it out of hand! That bald patch needs investigation!
The second thing is to find out how the species you are dealing with is functioning, so you can work with their instincts and not against them. Empathy, understanding and good bedside manners not just towards the owner, but especially with any pet you are seeing together with a thoroughness in considering all possible aspects are making all the difference between a good and a bad vet. I've seen either over the years, and I'd choose a general vet who cares for my pet anytime over a specialist who doesn't!
And thirdly, please be aware that you need to find a good vet for any neutering operation to minimise the risk of post-op complications or even fatalities. Ideally you see a general vet that is really experienced in guinea pig neutering or an exotics vet with lots of practice in small furries operations. I am not saying this to criticise you but because we sadly still have to pick up the pieces far too often on this forum when a newly neutered boar has a bad reaction to the GA or develops abscesses etc... It is always a very upsetting and often heart-breaking time for any loving owner.
Do you think that getting rid of Ren is really the right thing? After all, it is not his fault that he has been put into a situation where he feels he has to defend his leadership; he has been put in that situation by you.
If you want to take Ren out, then please have him neutered, so he can safely live with a sow after his 6 weeks post-op wait. That time is indeed necessary to absolutely prevent any pregnancies. The little baby in my avatar is the legacy of a supposedly safe over 5 weeks post-op boar (not one of mine!), just to prove that particular point. It can really happen as late as that, and my Tegan is not the only one.
Please do not fail Ren again by condemning him to a single life like those pet shops that have not the first idea of what makes the pets tick that they sell when they get a 'fighter' dumped back on them! Guinea pigs are group animals and not wired to live on their own, but any successful bond needs to be based on character compatibility and mutual liking, not on cute looks or being related. A shop cannot do that; that is why boars have such a hard time.
That said, a quartet is still the most unstable of all boar groupings. Unfortunately, when bonding guinea pigs, you always need to a have a plan B in case things don't work out the way you want them to.
