Hi these are my plants in the 1st picture they are 6 days old seedlings, the 2nd picture is 2 weeks old but the one im having trouble with, i have done my nutirent tab and the water ph is 6.4 i have the light on 20 hours on 4 hours off and the fan 24 hours these are auto seeds but as you can see its going yellow with brown tips. im new to this and cant see what im doing wrong i have been following the aerogarder guide on here. any help is appericated many thanks