I think genetics play a large role. The original poster was growing Jack the Ripper - I've had these "hash tips" on plants before, too, but always with Jack the Ripper, and often on mid to lower level buds as well. BTW - JTR is a mutant freak strain with a few genetic oddities like occasional buds on fan leaves, and extra blades in strange spots on the fans. It likes to flower in stages with multiple harvest "windows" (which is really fairly common for a sativa in truth). Interesting strain though, to be sure!
I've also light-bleached bud before, which can additionally cause trichome build-up. Makes me wonder if there could be a couple of different things in play that cause this behavior?
Like JJ mentioned, these seem much more common with LED grows for some reason, especially near the top of the canopy - I akways assumed those were a form of stress from light intensity, but seems like there is more to it perhaps.
I actually filled a really small nug jar with some of these from my last JTR grow, but they were pretty ordinary (to me) outside of looks...
is hands down the best website for information. I happened to come across this thread while experiencing the exact same thing with my White Widow plant. This whole time I have just been assuming that I had bleached the top being that it was one of the closer ones to the "LED"..Thing is, there were other tops in the same range(14 inches) , different strains, that were not experiencing this effect. I looked at the top today matter of fact with the scope, and discovered a mass amount of trichs covering the tip. This is all new to me, and a prime example of why this site is the shit being able to run across valuable info from other growers experiencing the same thing!!!Here is a pic of what mines looks like. Kinda be cool to have a whole white cola!! 
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