Dog advice please for my 2 male dogs

[LittleB]

I've got 2 neutered dogs; Rhubarb (Nova Scotia Duck Tolling Retriever aged 2.7) and Thistle (Border Terrier X just turned 1), (before anyone tells me off - I've had rescues in the past but couldn't find suitable rescues with my young dd!) Had them both from 8wks, when I got Rhubarb I also had an elderly collie x bitch who was pts aged 15 when Rhubarb was 6mths. Rhubarb has always been well socialised with other dogs - done puppy training etc, and has only had the odd disagreement when one tries to take his ball or bone. However he has always let Thistle take his ball from him. Thistle also well socialised, been to puppy clasees, never had a 'bad word' with another dog. Just recently there have been a couple of times when Rhubarb has had 'a go' at Thistle. They often playfight together, sometimes this gets a bit rough, and lately Rhubarb has been aggressive rather than playing a few times, he also snarled and snapped at Thistle the other day, when he was trying to take some food from Thistle - Rhubarb had already had his and eaten it.
I'm assuming this is due to Thistle reaching maturity and Rhubarb feeling more threatened, but I'm not sure what I can do about it, and if its just a phase that they will grow out of, or if its likely to get worse. Before I got Thistle I talked to my vets to see what they throught about having 2 males and they said it'd be fine if they were both neutered; Thistle was neutered at 6mths, and Rhubarb at 12mths. I just worry when I have to leave them, they have the garden and utility room when I'm out, they are rarely left for a whole day (they come to work with me), but often for a few hours, when I take dd out with friends etc. they always have bones to chew when I leave them, I worry that they might fight over them?
So far its just Rhubarb being aggressive, Thistle has never fought back, do you think they will just get worse, or might this just be a phase, anything I can do, and anyone got any experience of this?
I can't seperate them; Thistle gets very distressed when seperated from Rhubarb and cries and chews.

Bump, anyone with advice? Just had a walk which was really difficult; Thistle keeps trying to play with Rhubarb, but is typical terrier - jumping on him and chewing ears etc - Rhubarb just doesn't want to play, and had a go - I didn't see it, just heard a growl and a yelp from thistle - but then Thistles at it again within minutes. I tell Thistles 'no' and he stops when I'm close and I give him 'time out' on the lead, but he does it again as soon as he can. I don't want my softy Rhubarb to become an aggressive dog. Should I rehome Thistle -perhaps he'd be better off in a family with other rough and tumble terriers?

Interesting what the vet said about neutering both dogs sometimes it can be better to leave one intact and then the pecking order is set. But guess that is not an option now!!!

This could be a really serious issue so if things don't work out I would call a behaviourist in for advice.

First do not feed them together as this is obviously causing an issue

If they start to play in a rough manner you must stop this. I would use my voice to stop this behavious. They have to learn to play appropriately.

I doubt that they will grow out of it and will need to be shown what is the correct way to behave.

I would not leave them together even if they do not like it.

Do not leave them alone with bones ever

i'll think a bit more about this and get back to you.

Thanks for your advice minimu, I've phoned the vet for advice and they've given me the number for a behavourist, whose the same lady who did their puppy training claases so I'm going to give her a ring next week.
I cannot seperate them when I leave them, its just not practical - I got 2 dogs to keep each other company and my youngest will cry and cry if seperated - he's never been completely alone - they also come to work with me and often have to spend time alone together in the back of the car or landrover when I pop into the office.
But I won't give them bones now, and I can easily feed them in seperate rooms. I'll monitor their playing , and like you suggest use my voice to calm them when they get too rough - I do this anyway, but I think I need to get more vigilant about it.
Thanks for the tips.