The little leaves you are referring to are called cotyledons they are the false leaves. The spots on your leaves looks like a pH problem. Question did you presoak your rockwool in water overnight prior to putting your seeds in them for germination?hello. first i would like you to look real close at the first pic. there are some spots on the little guys leaves. wtf are they? i saw similar spots on some plants that were about 10 inches and died a week later.
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If used just for misting, 8.0pH won't be too bad. If at all possible, let the water sit out for at least a day (preferably 3 days) and you'll see the pH adjust naturally as the chlorine evaporates. Good luck mate
KC