Browning Pistils Already?

I've got 8 plants at day 32 of flowering and I have noticed browning pistils already. I figured it was too early for them to start browning but wasn't sure. I was also wondering what a pistil looks like once it has been pollinated if there is any change in the appearance. I am nervous about getting another seedy crop after my first one was pollinated somehow when all plants were female (or so I thought). I also bought Dutch Masters Reverse to kill male flowers so there should not be any. But I was wondering what could be causing the pistils to turn brown at only 4.5 weeks. Thanks!

Pollination is one possible cause, but the other common one is HEAT. High temps and drought cause premature browning.

Well, I was afraid you would say pollination. I don't understand how my plants are getting pollinated. I used that Reverse stuff and I have been checking over the plants very carefully looking for male flowers and I haven't seen any. I just don't get how its happening.

I really doubt it is heat; although my plants are within 2 feet of the 1KW HPS, I have an extraction fan sucking right up from where the bulb is, a small oscillating fan blowing across the bulb from the side of the hood, and a temperature higher than the tops of the plants and the highest it has read has been 85. I have been aiming the big fan up into the hood on the highest speed which usually brings the temp to around 74 or so. The rest of the room is usually around 70.

At approximately what point/how many weeks will I be able to tell if they are indeed pollinated?

After 2-3 weeks the calyx will begin to swell up and become bigger than normal. It will split when the seed is ripe.