It looks to me like you have your light too far away from your plants...What size MH are you using?

Don't ever put your vegging plants under 24/0...think nature. where on earth that is condusive to growing plants would there be "sun" 24 hours a day. the longest "Sun" day of the year I believe is just around 15 hrs...
plantsa need there rest, In order to have good photsynthesis.