Transmission problem

I need help with a transmission problem. I was driving the other day and came to a stop when I moved forward from the stop the transmission took along time to shift to second gear and it pulled out of first gear really slow and it was a hard shift. I did not think much of it since this is pretty much a new transmission that I put in it about eight months ago. I recently changed my filter, gasket, fluid about two weeks ago. I thought maybe it was low on fluid or something. I pull into the convenient store and check my fluid, it was a little low and pink so I purchased two more quarts of automatic transmission fluid and added that to the transmission and I drove off. It shifted a little smoother, but now it is acting up again. If I am cruising through the city it does not really want to go into second gear until I get on the highway where I can punch it, then it shifts fine and smooth just takes a tad longer to shift. Also my gas pedal feels pretty stiff, I am not sure if this is a torque converter problem or solenoid problem or if my transmission is going out? I sure hope not considering I just put one in it.