Not to worry.
I fill my tires every 2 weeks to 65 PSI also. I'll find the front at 50 and the rear at 45 PSI after 2 weeks and about 300 miles. I think the rear loses air a little faster because it sees higher pressure spikes while I'm riding and leaks out just a little faster as a result. I don't notice a huge difference in performance between 65 and 45 PSI.