I can think of a few things.
- Gently roust the yeast by tipping the carboy back and forth everyday for a few days. Avoid the temptation to check earlier than 7 days, but if your FG moved, keep doing it.
- At this point, make sure the carboy is at about 70 degree temps
- If you didn't do it; NEXT TIME aerate the wort after cooling by shaking it for about 2 minutes. The yeast will propogate much better. If you did do this, well, nevermind.
I've never tried nutrients, but gentle rousting and patience has always worked for me.