Hi - Did you tried opening the same server by different machine by mstsc? If not I request you to please try it out. It may be possible that the OS' brightness is working fine, its just a screen issue.
If you want we can have a web-ex session where I can try it out.
13 years of experience in developing enterprise level applications using ASP.NET MVC, ASP.NET, C#, SQL Server, Entity Framework, LINQ, WPF, WCF, WebAPI Development, SharePoint Development, Node JS & various JavaScript based frameworks like AngularJS 4.