After a hard styling, like we do at a beginners course, I've noticed that you can have a portion just die off (as Gerard said, due to the root work), and sometimes they just don't make it through at all... which hopefully isn't the case
I had the main branch on my tree die from my last beginners course, so it definately happens. Luckily I didn't really like its placement anyway

haha
Mine only get watered once a day in the arvo (I water foliage as well as soil on my juni's), and sit in full sun for the entire day. They don't really get any special treatment unless the temp goes above 40, at which point I move them into the shade. I seasol when I can, which is usually every month, and use a slow release fertiliser (as I'm still getting my fert. regime down).