My humidity is going up, not good!!!!! Please help! Thanks ;)

I have great airflow rn, but today my humidity just started going up, and it is concerning me. Its usually around (45-4 percent, and now its at 52 percent and climbing. I have my window open rn, and my temp is at 77 F I have one small fan in the tent itself, and a ceiling fan close by going etc. My plants are in a grow tent http://www.htgsupply.com/Product-HTG-250w--Small-Grow-Tent-Kit.asp Should I invest in a small dehumidifier? Put my window down? I am on day 11 with my plants, they are Purple Kush Auto. I am using 250hps for my two plants I have not watered in 4 days. I am going to water, and feed them today. Any help would be greatly appreciated Thanks!!!!!!!

I have the complete opposite, I don't have a control on my inline fan so it just runs full blast all the time and it takes the humidty right out of my tent, are you running the little duct fan that came with that kit cause if so I would upgrade to an inline and buy the control so you can adjust it. I bought my inline off amazon with a carbon filter for about 100 bucks. I'm new at all this myself so I cant give a whole lot of advice.

What's it supposed to be? Hydro?