Spruce Seedlings Keep Dying

Hi. I planted these from seeds that sprouted and then transplanted to another pot. I can't seem to keep them past this stage. Number one and two are starting to discolour and look like they're going to die. The third one looks okay right now, but they all popped up at the same time and this is the last from the seeds I have. What am I doing wrong? They are being watered regularly. Any ideas?

 

Potting medium may have unsuitable characteristics for these.

 

Possibly overwatered, and the potting medium perhaps not sterile, resulting in fungal disease.