I have a couple of white widow plants that grew together from seeds. It has been in veg for about 4 weeks. The leaves on bottom are starting to yellow. I looked iit up and found that its either ph or nitrogen. My ph meter reads 6.9 to 7.0 ph. I have been using a ph down to get the ph down. I flush the soil with 12-14 gallons of water around 6.5 ph. Within a few hours the ph is back up to 7.0. I assume its because I am using the miracle grow soil. Anyway bottom leaves are starting to look pretty rough. Yellowing leaves with green veins. White holes are starting to appear on the bottom leaves. Also this is my first grow so feel free to give me guidance on all aspect of my plant 
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