Get yourself a jewelers loop or small microscope and check the trichomes.
Look at the crystals and if they are mushroom shaped but clear this is not the time to harvest.
J
Although this may be good advice, I don't think this info applies to this scenario.
He said he's two weeks into flowering, pistils should NOT be browning in 14 days, infact, you're plant should be well on its way to robust bud growth, and buds should start looking white and hairy, not turning brown.
There's no benefit for looking through a scope at a plant that's only been budding two weeks. Furthermore, there's probably barely any trichs on it, if at all. I feel dumber for even having to mention this uber obvious fact.
Ok, Kriss, so my first thought is that maybe it's getting cold at night, what's the low temps been in your area the last few days?
If you're dipping into the 50s, that's pretty cold. Could be something else, but no photos or sufficient info to draw a solid diagnosis.