It's the shade of green; they are healthy now, for sure, and they don't NEED nutes right now, but they can definitely take and benefit from a stronger dose, assuming the light is good (which I am assuming it is, based on their extreme compactness). Lucas formula is great, I'd get them up to 50% ASAP; it looks like your babies are working on their 5th set of true leaves, so they could probably take 100% strength, but work up to that over the next week. Growth will explode soon, and I'm betting you won't have that Mg lockout you had earlier now that you're using distilled. You can switch back to tap if you use the Hard Water Micro, also.