My 2011 Ninja 250r is running 60mph at 8.2-8.3k rpms. does anyone know if it's losing power?

When I bought my 2011 ninja 250r I didn't over rev the engine during the break in period, and got my first oil change at 1k miles as per dealership suggestion. I was going 60mph @ less than 8k rpms. then I road it on a really hot day and I seemed to lose power. about 500rpms worth. sometimes it would get back up there but now it seems to stay about 3-400rpms less power than when I bought it. After careful thought and consideration, I decided to change the oil and filter at 4k miles... whoops, I know it should have been done sooner, keeping in mind that I road it pretty hard for a couple of days after I noticed lost power(hwy travel) =( but is it possible that maybe some seals got damaged or something, that could be the reason I seem to be losing power. Or could the heat and general break in, be the reason for the lost power? Im looking for an experienced answer. I would definitely be greatful for any knowledge on the subject matter. I really dont' want to take it to a dealer. also anyone that has a newer model 250r and wants to share there speeds @ rpms please let me know. mainly what your rpms are at 60mph. Thanks in advance!