newbie to growing, newbie to aerogarden

Hi all. I'm a first time grower using the aerogarden. My plants started out very good but now I've got yellow leaves on the top with brown spots. Some of the leaves are curling but these are on the bottom. I started out with one small nutrient tablet for the first 2 weeks and now I've decided that maybe I should have used one tab every week. My biggest plant looks like its about to croak. I just flushed the water yesterday and I turned the light cycle from on 24/7 to 17 on and 7 off with the pump off for 4 hrs a day. I thought possibly the plants didn't need to have the pump on all the time. As you can see from the pics some are yellow and one is dark green. Is this a lack of nutrients? I don't get it. Everything I've read talks about the leaves turning yellow on the bottom mine are yellow on the top leaves. It looks like the yellowing may be working itself down the plant. This is just some seeds I got out of my last bag. It was some excellent smoke so hopefully my problem isn't genetics but who knows? I just want to sort out this problem before I start on the good seeds I purchased. Any help that yall can give me would be much appreciated. I'll post some pics later today.

Originally Posted by "SICC"

She looks a lil hungry

Underfed??

This she looked before I put the tab in the water.. That first was 2 days after. I replaced the water and added liquid nutrients instead

Not that it is happier but.. is more of a social experiment.. grows among herbs