I've never had the problem so I've never had to remedy it myself. A friend used to get that, he fed at 1.8-2.0 steady. We used to run the same strain and I never had it. This was like 20 years ago when we started out. We ran same nutes, ph'd the same, similar environment, everything was the same except the EC/ppm level. I suggested cutting his feeds back and voila, no more burnt tips and hairs.
Had I had this issue a few years later I might have been able to pinpoint and diagnose through the mixing of my feed(as I started making my own fert mix) but it didn't so I can't really say which is the culprit. I would say it's just over feeding and a build up of excess fertilizer causing some kind of plant toxicity.
Less is more with fertilizer, #1 rule. Overfeeding just once can cause lock out. I don't know why but I used to see it with alot of my friends, they felt like if they hit it with more Monster bloom it's magically gonna make the buds bigger. The thing is the plant will only eat what it needs,n that is the ratio that I mentioned earlier. Anything extra is just gonna build up n cause a lock out.
Hope this helps some folk. Less is more!