The yellowing is the plant just saying its hungry so feed it. People treat hempys like soil and they are not. The way I do my hempys is I condition 3x3 rw cubes in a 300 ppm lucas feed ph'd at 5.6, plant the seed and cover and set it on my water heater. I nearly always have a happy sprout 36-48 hrs. Uncover the seedlings and place them under a cfl for about a week until I have an inch or so of taproot out of the rw cube. The rw then goes into its final 3.5 gal container of 100% perlite and put under my mh. Feed daily with 300 ppm lucas for 1 week and then start bumping the feed 150 ppm a week of whatever base nute/additives you will veg with, 1 gal every other day. Feed every time, the runoff is plenty to flu I have had mutant leaves on plants a couple of times and while they look cool, iv either had a bad plant the entire grow and regret not pulling it or have it herm and regret pulling it so I don't grow anything out that's not solid anymore.