Your setup looks cool man. Re yellowing leaves, yes overwatering can indirectly cause it. When you over water you are rinsing nutes out the soil, also your plants root cant breath, then they struggle with nute uptake and then you start seeing nitro deficiency. So it can cause it in a roundabout way. It could also be your temps, in cold temps the plant will struggle to uptake nutes so again yellowing leaves. Here is the important bit... I think your plants look fine. Just maybe lay off the watering a bit, feel the weight of your pot, and then feel it again in 2 days. Only water if it feels light. One other thing, if you have more lights and are thinking of adding them, do it. There is no such thing as too much light. There is only too much heat, so as long as they don't cause your box to heat over 90 I would use them. Good luck.