If you continue to run two servos from the Arduino you may damage the Arduino or your PC.
Things like servos and other high current loads must be powered by their own dedicated power supplies.
These power supplies need a common GND to the Arduino GND.
I believe your version runs best at 6v but will probably work fine at 5v.
Suggest you use a 6v/5v @ 2Amp power supply for this application.