Try explicitly defining with parameters along with the updated targets. This can generally cause the windows to be "popped out" as opposed to opening in tabs and hopefully should cause them to not override one another :
window.open(this.graphicAnalysisResource,'_blank','height=500,width=500'); window.open(this.graphicAnalysisResource2,'_blank','height=500,width=500');
You can see an example of this, which should be working properly here.