I have nothing against Miracle gro, but it's possible you got a bad bag of soil. This once happened to me with another premium brand -- it even killed chrysanthemums I tried to grow in it. All the problems disappeared when I got rid of the bad bag of potting soil. It's happened to me only once and I've been through hundreds of bags of potting soil. Rare, but it can happen.

There's also a new type of MG soil with water retention crystals. Don't know how much longer it holds water, but IF original rootball was really small but really wet and IF you put it much larger pot and IF you watered it a whole lot -- is it possible it just got waterlogged that's what killed it? I have all those "IF's" since I don't know what conditions were. Just a thought....

I have to agree with brit... the moisture control miracle gro (it doesn't use moisture crystals, but just coconut coir with a wetting agent) can be really tough on small transplants. I had the same problem with my parsley, until I stopped watering so much. Once the roots had established themselves, it began to grow like a weed :)

I've done better direct sowing my parsley. Just scratch some soil lose, put some soaked seed down, sprinkle dirt on top, a little bit of mulch and mist every day.
I sow in the fall, around October here in AZ. I now have a constant patch that reseeds itself but I plan to start several more this fall, since it attracts more Benificials than anything.

I direct sow parsley as well. Other than it taking a while to sprout and me thinking it failed, no problems at all with the direct sowing. For me I usually sow in the spring. Though I had a patch seed themselves in last fall. It has oodles of tiny parsley plants this spring.

FataMorgana