This goes out to Sungha Jung as well as anyone with knowledge:

I've been learning a lot of Sungha's songs, and as we all know, he likes to go into different tunings. Well I have ran into some trouble:

When down tuning from standard (i.e.: to DADF#BD, DGDGAD, etc.), my strings have popped – specifically the G and high E. WHILST tuning down. I asked for some advice at my local guitar shop, and they told me to put in some pencil lead into the nut slots. I did that and although the strings slid a lot smoother, they broke nonetheless. I have inspected my nuts and they all feel smooth.

I figured since Sungha goes to different tunings constantly for different songs, he could help me out. Or maybe some of you guys are learning his songs too and know the trick.

This has happened to me 4 times already – x2 on the G and x3 on the high E.

Guitar: Martin 000-15m
Strings used: Martin SP Lifespan, D'Addario Phosphor Bronze Light, Elixir Nanoweb Phosphor Bronze Light

*The strings have never popped while tuning back up to standard, always down.
*The strings don't even last a month before popping; the Elixirs popped within 6 days.
*I downtune and retune at least once a day.