Were Nox and Tucker neutered just before arriving at your house? Or just after?
Some neutered dogs seem to have it in for intact dogs. The theory is they are jealous but no one really understands it. It can take up to six months, in my readings, for testosterone to leave a neutered dogs body. So if Nox and Tucker had only recently been neutered they might still have smelled very intact to Ryley.
Especially if they were neutered at around 7 to 11 months when testosterone levels in a male spike to 3 to 7 times what they will be in adulthood. At this stage in a young, intact male's life any dog is likely to see him as needing to be put in his place but particularly that neutered male who sees all intact males as a threat. It's well documented and it might explain why adding a neutered male dog to your family IS the same as adding an intact male.
At the link read down to Puppy License to Misbehave.
Now none of that really helps other than to explain why it might be happening, if the timing fits. If it does then I wonder if because the dogs are constantly together Ryley just never gets over seeing the other two as a threat. I'm sorry, I have no idea if it will work itself out. I wonder if a new dog well past his neuter would face the same reaction from Ryley.
Good luck. I hope you can work it out so all can live in harmony.