wow, sounds like you have alot going on! im sorry this is happening your first time, but hey you gotta start somewhere, dont get discouraged! I think you can get alot more help with a better quality picture or maybe just a few more. But Based on your one picture and your description, im gonna go ahead and say it has something to do with your soil. if you're not feeding it nutes already with your water (which you shouldnt yet), not overwatering (making sure your soil is completely dry at least an inch or more down before watering, not just one time, but between every watering). My last 2 guesses having to do with your lighting would be your 600w light is too strong for your plant, maybe try raising it up quite a bit and monitoring its progress, 600w for one plant sounds like overkill. Or that Switching from your florescent lights to a very strong 600w MH shocked your plant and then your efforts to fix the problem is just making it worse. UNLESS your soil has some type of time release nutrient (garbage) idk ive never used fox farm. But I would just raise the light quite a bit, regulate your watering more, and see what happens. This is all i can really say for now based on the picture, maybe theres something on your leaves that could tell me more, but for now thats all i have for you my friend. best of luck!