Brown pistils

No, it is not a problem and perfectly normal. The older calyxes are maturing and the brown pistils are a sign the ovule inside the calyx is passing its viability to be pollinated and therefore, fertilized. The white pistils associated with the youngest calyxes at the top of the flowers are obviously the freshest and most viable for fertilization. The brown older pistils may be less likely to "catch" pollen rather than the fresh softer pistils that are white and this may be a way how cannabis has evolved to prevent old and less viable ovules located at the base of the pistils from becoming fertilized, in preference to the younger and fresher ovules in the newer calyxes. Hope this helps, .... Organoman.

Sativa/hemp strains in the genetic blend tends to have brown pistils early especially with heavy feeding. As long as you are getting the cola to weight more, this is an excellent trade off. For this sort of strain, nugs are fluffy compare to Indica dominant strains. And flowering time may drag on a bit longer. So, I actually would back down on my feeding a bit. Definitely don't ramp up feeding toward the end. Most likely, flowering time would be 10 weeks. So, you will only need to feed your plants for 3 more weeks. And if you haven't don't so already, please look up molasses and how it helps with nugs quality.

trichomes are one of the indicators to determine when to harvest. They will turn from white to a dark color @ the end. These are naked-eye visible, the next step is to use a 60x microscope(the digital-PC-connected are awesome) to check the trichomes. For a head-high effect Harvest when trichomes heads are cloudy and about 10 or 20% just turning amber. Its best to make the Harvest after a night just before it's time for the lights to turn on.

5 weeks into flower.. No could definitely be a genetic trait. If she has shorter flowering period this would be about right.. Start checking them Trichomes. I mean she has weeks left but the brown pistils are usually a sign that those parts of the plant are maturing so you should see the trichomes start to pop a little more. looking good lots of bulk there should be a a real good haul for you.