These leaves are pretty pale green ... what's...

Looks like too much water and too much light to me. The leaves are puffy sagging and have bumps from the excess water. The light is showing in the tight node spacing and smaller leaves. I would water less and raise the light up a foot or two

Hey there, a nitrogen deficiency can cause the lower leaves to turn a yellow color, and eventually they will die off or fall off. Typically if you're deficient in a nutrient, its often more than 1. I assume your giving a micro nutrient formula with your others? I think the micro is safe to give more of and more often since they usually have a low NPK. I hope the problem stops and gets better happy growing.

HI mate, Looks like the start of nirogen deficiency. Low nitrogen is generally characterized by an even yellow or gold color of the lower sun leaves. Slow growth and undersized leaves and red stems are also clues. Adding a high nitrogen fertilizer should remedy the situation within a few days and will be accompanied by green, lush growth. If you give any nutrients start at half or quarter strength. It’s not cal/mag but if it was, such deficiencies are rare so early on with pre ready soil, symptoms of spotting will first occur on new growth and your marijuana may appear stunted or have slow growth. Remedy by using Cal Mag. Try using tap water instead of distilled or RO water. Very rare in soil grows, symptoms of magnesium deficiency occur first on the lower leaves. The stems and petioles will turn increasingly purple. Fresh growth may appear lime green. There may be chlorosis between the veins on the leaves and the blades may begin to die and curl upwards. White leaves with green veins may be an indication of a severe deficiency. Treat with Epsom Salt and your weed will recover in under a week. Hope this give you more of an idea not only for now but for future reference. Feel free to drop me a message if our need anything. Other than that you plant looks fine and those are some nice Sativa dominant leaves. Keep on growing buddy. ✌️

Hi bro, this doesn't look so bad to me, I would wait a couple of days before taking any decisions, but this could be related to Magnesium deficiency and/or Nitrogen deficiency. I'd recommend to upload new pictures once the symptoms will be truly visible. I'll be around, good luck with these babies!