HMMM..while I agree you could use more light...who could'nt right, you can never have to much. The issue I see in your OP is the MG soil w/ Fox Farms trio. Have you been using the nutes full strength? If so I am happy for you that they are as healthy as they seem to be. MG soil is not bad but alot of growers have issues with it. I do not use it myself, but I have in the past. Grew very nice plants but MG soil can be tricky and is often missused by over-watering and adding additional nutes. If this were my grow I would stop the nutes, prune the dead leaves and let them finish vegging. After switch to 12/12 I would start the trio at 1/4-1/2 strength (closer to a 1/4 better to under nute than to over nute). I also would not increase the Grow Big solution more than 1/4 dose. It is high in N and will keep them nice and green but the soil nutes have a lot of N as well. Best of luck!