1st grow....HELP!!!!

Ok I started a month ago with fluros only 2, then a week later (3weeks ago) I added 2 more for a total of 4 fluro's. I just got a 250w MH and HPS with digital balast yesterday. I have a fan on them and heat isnt an issue. However there are some light yellow spots beginning to show on my leaves, so I backed the light off about 8 in. Can anyone tell me how far away a MH should be???What are the yellow spots on my leaves?? And What kind of yeild should I expect to see from these bag seed???

When they're young try not to stress them, when you change lights try not to stress them. Keep the MH lights about 24 inches back till they get acclimated. The yellowins probably a nitrogen defficiany. Try some fish fertilizer and it should green it back up within 2 weeks.