Dill is by far the LEAST successful herb in my first herb AeroGarden. From the start it was slow growing and turning yellow. I have read other people's comments about Dill being their fastest grower (until the Basil catches up) and needing lots of trimming to keep it out of the lights.
I found my problem.
My water, I use RO water, is acidic, apparently more acidic than most. Also, the AeroGarden nutrients, and perhaps the plants themselves, seem to make the water more acidic over time. Dill is apparently the most sensitive to low pH of the plants in the AG nine pod herb garden. (Italian parsley is also sensitive and new growth is yellow if the pH drops too low.)
I bought a pH tester and pH up (and down) solution. When I raise the pH to 5.5-6.5 the new growth instantly goes back to that nice green, but the part that is yellow, never recovers. I have been able to save the dill but unfortunately it is never going to be what it could have been.
Thanks sher01. Most people probably don't have this problem. Maybe you don't need to check. I certainly do. I have to check pH very often (every few days) or it creeps back down. The yellowing dill was, sadly, not just a one time thing. I have let it happen about five times in the 109 days (just checked) since starting. I really have to keep on top of it. It is a miracle I have not killed my dill yet.