Having issues with Lightroom adjustment brushes..

[TamiAz]

When I try to use my adjustment brushes in LR It changes the whole image.. I'll click on the area where I want to make an adjustment and this is what happens. Do you see the darker box?? Then the entire image will change. I got a new monitor today and I calibrated it. I'm working on my Mac book and using the external monitor. What could cause this?

 

[TamiAz]

I turned off the external monitor and unchecked the "mirror display" box on my mac and LR runs perfectly. So, it's related to using an external monitor and I don't know if it can be fixed.. Has anyone experienced this with LR?

 

[TamiAz]

I figured it out.. I had to make the external monitor as the main monitor instead of checking the mirror box.