The hairs (pistils) purpose is to catch the pollen from the male plant and then the pollen spores will grow down the pistil to fertilize the ovule (embryonic seed) located at the base of the pistils. The older the ovule, the less fertile it becomes, with a corresponding drying up and browning of the pistils, which are then less able to catch pollen. This way, only the freshest and most fertile ovules have the greatest chance of being pollinated/fertilized. Therefore, the whiter the pistils, the "fresher" the ovule. Conversely, the "staler" the ovule, the browner/more dried up the pistils.
In human terms, once the pistils have turned brown, the ovule is past being fertilized and that calyx/pod/bract holding the ovule and pistils, is equivalent of having reached menopause.
So, the fact that some pistils are turning brown is completely normal in the cannabis reproductive cycle and is not an issue for concern, it is just that those calyxes/pods/bracts that have become too old to grow seeds.
Yes, the white crystals/trichomes are what contains the THC and other cannabinoids that get you high, and are also a good sign of the plant ripening and maturing.
Aroma can come and go throughout the flowering cycle depending on what type of cannabinoid synthesis is occurring at that time and will eventually increase in intensity as the flowers ripen, Again, this is a normal part of the flower maturation process.
Sometimes the lack of smell is because we as humans get used to the smell and don't notice it as much anymore, a bit like a person who works at a fish market and can't smell anything fishy anymore. Invite a friend over and I bet they will say your plants stink!
Hope this helps, Organoman.