Rust spots on leaves?

To me it looks like burning caused by getting nutrients on the leaves while the lights are on. Once the water evaporates, mineral salts get left behind and can cause the blotches like you have on those leaves, especially previously dissolved calcium. You will need to start feeding them with some (1/4 or 1/2 strength) grow nutrients soon, cal/mag is not a growth stimulant, your plants need nitrogen, phosphorous and potassium to grow, these three are known as major nutrients. Calcium and magnesium are both known as minor nutrients and are needed for healthy cell function and none of the minor nutrients provide the substances for growth on their own. Hope this helps,.... Organoman.