Hey again I got another question about my 4 year old JRs.

Basically, my dogs fight (may not be the right word but I don't know what to use other then that) all the time with each other. Sometimes its just nips at the leg when they are laying down and they don't seem to care much.
But sometimes they both at trying to bite each other and all, I see the female grab onto his neck and just hold him there and he doesn't seem to be in any pain or whatever. He does fight back, it looks quite cute sometimes.

How can I tell if they are play fighting or actually fighting? Because I never have heard them let out a yelp or screech of pain. So I never thought of it.

I wouldn't worry if they are not getting hurt. Sounds to me that they are just playing. :)

Odds are they are just play fighting...
Do they chase each other around as well?

Does this happen when one has a toy or food or just randomly?

If one growls at the other and nips when it has a toy or food then yes, it sounds like it may be serious but if they are chasing each other and not biting hard then it is just playing.

They do chase each-other and the female does do that "play-bow" when she is about to run. I know that they definitely growl when they have a toy and the other wants is. Its mainly the male that growls when she wants to take a toy off him (shes really persitant with it) his growls do sound serious enough to make me tell off the female.

You could invest in some training classes to help your males aggression towards toys.

However mine do that though except the other way around. My female is possesive of toys when my male tries to take them from her.
My male knows to back off though, once she growls at him that's it, he walks away.

It could turn serious one day if she is persisting while you are not home so I would start training with both of them.

The fact that they do play with each other is a bonus as the aggression is only when he has a toy, not all the time.