How big are they? Sunflowers grow so fast that they run out of food and water very quickly.
I'm having the same problem, but I thought it was because I'd overdone the plant food..?
You shouldn't really be feeding seedlings for the first few weeks - potting them on into fresh compost as they outgrow their pots should give them enough food.
Yeah Lesson learned on that one...
I may have left them too long in the cells but the weather has been apalling in this area for weeks. The plants are about 8 inches tall and are in cells about 3 inches deep. If its a water/feed problem will they grow out of it ?