Yellowing leaves near top of plant and lower plant.

So I know blurple pictures aren't really that beneficial as it doesn't show the actual coloring of the leaves so im sorry but the symptoms of the yellowing are more prominent when the light is on compared to when its off so thats why I included it with the lights on. None of my healthier older growth looks like that and only newer growth on the bottom of the plant seems to be getting effected for now and then obviously the new growth at the top canopy of my plant is starting to yellow. I believe it could possibly be that my light is too close but ive slowly been developing this issue now over the last week or two is it possible that it is a mag deficiency instead since in starting to get into preflower? I just wanna make sure I get this baby to harvest even if my yield is small I just want to do it so I can learn better next time. Thanks in advance. In due for another watering here soon my ph meter doesn't test ppm so I bought another meter coming in the mail here soon so I can get a better understanding on if im out of range there. My light id say is about 8 to 9 inches from my plant I know that's really really close thats why I think it could possibly be that too but I have no way to currently hang it higher so if thats the issue then I might just be S.O.L until I can figure it out.