Yes , with it being frequently and the presence of mucus possible respiratory infection. See a Herp vet , one that actually treated turtle's before. Do not wait for other sign , needs "early" treatment for good results. If one waits to long can go into Pneumonia which in many cases is fatal. There are no OTC drugs for RI. Until the appointment I would raise the water temp to 80* and basking area to 90*-92*. This will help ease your turtles discomfort.
Good read :
http://www.redearslider.com/respiratory_behavior.html