I have done a lot of experimenting with growing these things. (sarracenias) I have several 1000 seedlings so I can afford to loose a few. I have tried all sorts of mixtures and I have found the ones with the greatest proportion of LFS (long fiber spaghnum) do the best. A deep pot and air circulation to the roots is somehow important as the first roots tend to streach for the water table. At first I thought that they were slow to recover from disturbance, not true especially on the young ones. Some of my seedlings are 4" tall and are only 6 months old. I have some that are a year old and 10" tall showing fine coloration. Now, I also have pushed them hard. During the winter they were under grow lights 24/7 and fed every 10 days. Indeed you can fertilize. BE CAREFUL! I have burned some of my best seedlings. I learned that you can feed from the Atlanta Botanical Garden. They grow sarracenias as part of their conservation program. Their mixture is as follows: 20-20-20, 1/8 teaspoon per gallon for seedlings applied with a mister once every 10 days while actively growing and not while in direct sun. Only lightly mist the foliage. Do not soak the soil. Shake the bottle! I try to top flush the soil with rain water to wash an residual through the moss after they have dried or over the next few days. You can up the solution to 1/4 for adult plants and follow the same guide lines. All that said, I also have seedlings that have just sat or have actually declined. I would transplant them personally. Good luck and keep us posted.