In that case, don't mess with the nutrients unless you see the fermentation stall.
If it does stall, add it carefully, once you add it will take off like you added an alka-seltzer tablet to the fermentor. It will bubble like crazy. I did this with 2" of space from the top of the carboy and I was lucky it didn't roll out over the sides. It was brimming with cider. I recall I also tipped the carboy slightly since a good bit stuck to the inside of neck of the carboy.