Answer: That's a puzzler. If the seedlings survive without long-term effects, the problem may be a temporary fungal infection - perhaps from overcrowding or too much moisture/humidity. You may be moving or transplanting the seedlings just soon enough to change the environment, making the fungus die off. Or the infected leaves might fall off before they've had an opportunity to spread their disease. If the white spots are not diseased, but a symptom of sunburn, perhaps your indoor lights are too close or too hot and they're magnifying any water droplets on the leaves to the degree that they're burning the tissue. Pay really close attention to lowering the humidity around the plants and giving them plenty of good air circulation to keep them healthy.
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