I assume that the temps are F and not Celsius. As TRD has mentioned your temps are too low and you're most likely still too rich. Befor you start leaning it more tho, try and run it harder first. It sounds like you may be a little timid with the throttle still. If it's broken in (which according to what you wrote, it should be) you will be fine. Give it some juice. Bring that temp up and then check and see if you need to lean it out a bit more.
Also, don't forget that you have an idle adjustment and low end needle as well. Your low end might need to be leaned. I've noticed that some don't pay much attention to low end and idle, that's all.

Traxxas makes a good fuel for RTRs btw, so you can just stick with that.