RPM higher than normal

I have a 2012 Toyota Tundra SR5 TRD with 115,500 mile and have been towing our RV trailer (in tow-mode) my last trip I noticed my RPM's were approximately 500-1000rpm higher but yet the same exact speed. I have found that when I'm traveling 55 - 60mph my RPM are consistently at 1400 - 1800. This past trip same speed, I'm now seeing 1800 to 2400rpm. I'm not a mechanic but have always have the fluids check every 5000 miles. Is my concern warranted?
TYIA Norm

 

Simple things like ambient temperature higher, minor weight increase, tiny bit of throttle increase can have it drop a gear.

Next time place it in manual mode and take note of what gear it's in. It seems like it dropped down a range.

Last little bit, fuel quality could also play a role in its gear selection.