Cannot get windows screen to 2560 x 1440

Hello I have a mac with 3 27" monitors and I am running parallels 6. i cannot get my resolution any bigger than 1920 x 1200. is there anyone who might be able to help me? Thanks

If I am posting this in the wrong area could someone direct me please.

 

* Install Parallels Tools if they aren't already installed
* Increase Video Memory in VM configuration.

 

it is set at 256 mb. that is a big as it will allow me to go.

 

I got it work haha! thanks. What I did was in windows under Advanced settings / Monitor I unchecked the box that says to Hide modes that this monitor cannot display. that did the trick. thanks for your help.