White spots on a few leaves

That doesn't look like a nutrient issue, but more like you have spilled water or feed onto your leaf and it has either been burned. With plain water it can act like a magnifying glass and concentrate the light in a small spot and burn. With feed, as the water evaporates, the mixture becomes much more concentrated and can burn like this. Simple to avoid, don't get water or feed on the leaves, especially not when lights are on.