I think this may be as simple as you have the foil shiny side out.

I think shes getting flash burn.

Swap it around.
HARDDON Reviewed by HARDDON on . What does this discoloration mean? This plant is a week and a half old since seed. The leaves started yellowing in the middle with the darker normal green concetrated towards the stem. The tips of the secondary leaves are yellowing too. This is happening to 3/4 of my plants so figured I'd ask. It looks less yellow in the picture than in real life. They are in Sunshine Mix #1 being fed 6.0 water, switched to 6.5 today. No nutes have been added yet, just superthrive in the water. Temps are around 75-80 with CFLs. I have Rating: 5