Yeah, I have to say hot soil. It doesn't matter if you have added nutrients or not, if there are time release nutes in your soil, they will burn the hell out of a seedling. Always start with a very light soil and then transplant to a hotter soil after your plants have the root/leaf structure established well enough to handle higher doses of nutes. Even Fox Farms Ocean Forest is WAY too hot to start seeds in.
It is critical that you tell us what soil you are using.