Jason,
I don't believe I am a great trainer but I do believe we could do with more participation here. So here are my thoughts.
Often our individual problems require a little bit of innovation. If I had a similar problem I would probably try something like this.
In light cover set two throwers 10 mtrs apart throwing in oposite directions and using white dummies.
< 10 mtrs >
This should have the birds about 50 mtrs apart. Now take the dogs back 30 mtrs. Do it as a double, in light cover the dog should have no problems. Now using the same set up but retreat 60 mtrs. And then 90 mtrs. Once you have done that call it a day. Do this a couple of times in different areas. Then using the same set up (different area) start at 60 mtrs, then after the dogs a successfully doing that start at 90 mtrs. Finally work this until you can do two reps starting at 120 mtrs then one rep at 150 mtrs.
This starts the dogs a wide angles reducing the influence the birds have on one another and the light cover ensures an easy fast find. I would think every day for up to two weeks, let the dogs set the pace. Vary the order of throw and the order of pick up. How long the dogs have been doing it poorly will determine how long the fix will take. The more thorough you are the better the fix.
From here you could do any one of three things:
a. repeat the process in medium cover,
b. repeat the process in light cover and vary the angle of the throwers so that one angles in, the other away, or
c. combine both of the above.
Don't rush let the dogs progress determine what action you take.
Good luck
Graeme