I grow both of those almost exclusively and they both look really good. Looks like you got some good genetics, which is very important and very rare. The Diesel will prolly out stretch the GDP by the time theyre done. You'll be amazed at the yield difference too. Diesel is a huge yielder if you do it right. But they both can handle almost anything you throw at them, so push the nutes the further along in flowering you are. At week 8 for the Diesel and week 6 for the GDP I'm at about double recommended nute strengths. And yes, node distance is determined by the light distance, but also the type of light. MH's will always stack nodes, it has to do with the spectrum. HPS's will always stretch a plant more. But like I said, good job. The 'only' thing you way wanna do different is not bring them outside ever. If you have a clean and pest-free room, you really dont wanna bring something in just because you wanted to take a pic. LOL