I planted green lettuce in my Smart Garden 3 almost two weeks ago. It has been growing really well and fast, except for these little small dots that have been appearing on the leaves. It first started as what appeared to be burned edges on the outer leaves, so i figured the light was too low. After I added the light extension, everything seemed fine but then these little dots have appeared on the leaves. I cant seem to find any bugs, or fungus. What can this be???