Sounds like they were installed without a pressure balancing loop. That's an open the wall up fix.

Thanks LWO--I had thought of that but the manufacturer's installation instructions say that a pressure balancing loop is only necessary when installing four or more.

I use a loop when plumbing two or more sprays. I'd rather use an extra $10 of copper when the wall is open than have to...you know.

If they haven't always been this way, that's one thing. Then it could be debris or mineral deposits.

If they have always been this way, then you could try to fiddle with them by modifying the flow restrictors in the strongest and/or weakest sprays. See if you can find a Goldilocks solution.