tranny slips shifting to 2nd

My car has 84,000 mi. I have noticed for a few months now that when my tranny shifts to 2nd under light throttle it shift way too hard like a WOT shift. Also intermitently it runs the rmps up too high then shifts.I recently droped the pan and inspected the fluid changed filter, looked a little darker than new but ok , smelled ok, no shavings . My question is do you think that my tranny is slowly dieing. Do you think I need a rebuild, Or could it be something simple? Thanks, Anthony edit it only slips 1-2 shift shift fine after that :)