Week old seedling dying? Pics in thread

[Toke+Choke]

So I'm exactly a week in from planting germinated seeds it's fast and vast auto.
As you can see below one is thriving and one is seriously struggling.
Info....
300w dual spectrum cfl
100m3/h intake
180m3/h outtake with carbon filter
Clip on air circulation fan
12L final pots from the beginning
Gro-sure vegetable soil mixed with perlite for a lite soil mix
Been given nothing but water at this point not going to introduce nutes for another week yet!
Can anyone point me in the right direction please.
Is it just a duff seed?
My other two plants (train wreck autos) are also fine.
Thanks guys n gals.

 

[Moldy]

The "sick" one shows no perlite present and the soil looks wet or sorry to say muddy. I think you need to get more air to the root(s).

 

[Hotboxbudz]

Transplant the little one into a soil with 1/3 perlite, 1/3 peat moss and 1/3 worm casting. Water every 3-5 days (or when needed).

 

[Toke+Choke]

The reason it's got no perlite on top is because I transplanted it into a smaller pot to use the rest of the 12L pot it was in to top up my other 3 pots so now the soil is only half inch below the leafs instead of 1 and a half so I've got more rooting space for the other 3.
Hope that makes sense.
It was in exactly the same pot as the others until this morning.
I think it's a goner!