65% humidity isnt a large problem but it might not hurt to drill a few more holes for ventilation.
In regards to your advice from the pet store, they prolly could have been more discriptive, least how RI infections are caused. But the pet store could have been correct if the current discription you gave them was accurate, it does sound like a mild infection. Bumping the temps and lowerin the humidity down to 50% should suffice. However, a call to the vet may be in order. Even in mild cases. I have dealt with mild RI's with my herps and bumping the temps to 95 and lower my humidity worked for me in the past. Ever senerio is different so what has worked for me, will not be the same for you. Please keep that in mind.
Now, it would help tremendously if we could have a better discription of your husbantry. Sounds like thus far, you have it housed in a rubber enclosure which is fine. But RI's aren't just caused from low temps. A damp subtrate, drafts from window, open doors ect can also be culprits.
You really should get a digital thermometer, the ones people often use in households to measure temps inside and outside of the house. You can find them at radioshack, wallymart, home and garden stores and internet.
I use this thermometer myself and it is awesome! I love it because I can measure the heat left from right and humidity. Plus it records the temps dropped over night and the highest temps reached so I know just how much my temps were flucuating while I was away. Great little unit.
Edit
I should also add in addition to digi. thermometers in my enclosures, I also have a digi thermometer mounted to my wall to accuratly measure my ambient temps. This is also important in my humble opinion because ambient temps will often effect temperature fluxes in enclosures. Moreso at night. Most people have there thermostats to their house set to drop at 68 degrees. Something that is overlooked and also a prime senerio for RI's develope.
Good luck friend.
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And that is not my arm.