First Grow - LSD DWC

This is my first grow. I actually smoke very little, but I'm interested in the science behind growing, so for me, this is like a chemistry set for big kids. I wanted to jump right in to slightly more advanced growing techniques than most first time growers. I know there will be a lot of errors along the way to correct and improve upon, but that's how science works and that's what attracts me to growing. I'm disappointed that I don't have a set up that is appropriate for supplemental CO2, but maybe I'll build something else if I stick with the hobby. I've probably smoked less than an ounce in my life, so I'll hopefully have the problem of figuring out what to do with my extra product at the end of all this. I actually started about three weeks ago and promptly murdered 3 of 4 plants. One stunted girl survived and I started two more seeds which are doing much better, so I actually have one plant at 3 weeks and two at one week. I started the first plant off in rock wool and the switched to Rapid Rooter for the other two. I sprouted the seeds by soaking them in water for one day and then moving to the paper towel method. All the seeds started roots within 24 hours of being in the paper towel. They then went into a humidity dome and from there were moved to their 5 gal DWC buckets when the second set of true leaves started to come in. I'm using distilled water. I started off with pure water and then slowly the PPM up to 100 over several days. The older plant is at 300 PPM. I'll work on lighting that doesn't over expose my photos so much and shows the color better next time. The light is a Mieemclux 1500 LED. It's a cheap burple light from Amazon. I have a relatively cheap Hydrofarm PAR meter and while the light does provide good results directly under it, it has almost no spread at all. The PAR drops way off just outside of the space directly under the light. I originally ordered two of the Mieemclux lights, but after testing its results, I sent one back and ordered two Mars TSL 2000 Led lights. Hopefully they'll get here before the plants outgrow the area directly under the current light. I've got the plants at about 500 PAR right now. You'll notice that the older plant has some brown spots on one of the leaves. Those have been there since I almost murdered it along with its sisters on my first try. All the other leaves came in fine and I haven't seen any other obvious issues. We'll see how this experiment goes. I'll work on having better lighting to show true colors next time.