BRO! Your plants look great! Let me ask you a question. When you turned the lights back, naturally you changed ferts to something high in "P" Phosphorous(N-P-K) , correct? It might not be overfertilization, but lack of "N". It's normal for the bottom leaves to start to turn a little yellow in flower but people tend to get a little crazy with the Phosphorus when flowering and leave out the N and the K which the plant still needs, just in lower doses. This is something I copied a ways back. Don't remember who to give the credit to.
"A common mistake for growers when they reach the flowering stage is to start hitting the plants with a high P fert like 10-60-10, continuing to us this blend exclusively, and when their plants start experiencing a deficit of N or micros as reflected by the dropping of lower leaves and chlorosis, they wonder why. Plants flower as a response to long nights, not because of fert blends high in P. A ratio of 10-60-10 is wat too high in P. The plant will only take what it needs and compete for the other elements that may be MORE IMPORTANT at the time. You may have heard that too much N can inhibit flowering. No question about it, exclusive use of a plant food that is rich in N such as Blood Meal, a 5-1-1 blend, or ammonium nitrate may inhibit flowering especially if the Phosphorus level is low, but most balanced blends have sufficient amounts of P to do the job. Using a high P fert exclusively during flowering can actually work against you. It's an abundant amount of healthy leaves going into 12/12 that produces a lot of buds, not high P ferts."
