I planted some nectarine seeds a while ago and they have been growing slow but steady for the past few months. I have 4 smaller (approx. same-size all of them) plants and I've seen that lately the leaves of two of them are turning yellow. Even with a redish tip. What could be the cause of this? I can't see any bugs or attack of any kind. These plants are placed indoors with a constant temperature or 18-20 deg C. During the previous months (winter here in France) they have received limited amount of sun.
What could be the cause? Too much water? Too little water? Nutrient deficiency?
Thanks in advance!