A lot of reasons... An decreased of total visits may mean you may not have promoting your site as aggressively as last month. An increased in new visits may mean search engines are referring you more traffic.
increased in new visits may mean search engines are referring you more traffic. i'm not agree with you bcz new visits means if today your site visit 100% country with USA so if tomorrow in your site 90% same country people will visit and 10% you got new visit with other country that means New visit
Increasing new visits means unique visits and decreasing total visit means unique + revisitors are less than before
Check your content and post some good and unique content on it do onpage and offpage optimization for your site. promote your site in social networking sites. You will definitely get good and unique traffic from it.