They are african daisy, pansy, snapdragon and other flower seedlings that were started indoors under lights, moved to a small greenhouse and then placed outdoors. They are still in cellpacks waiting to be transplanted into the ground.
Have they outgrown the cell packs? sounds like a great start and they probably should have been transplanted to bigger containers once the 2nd set of leaves appeared. Did you place them in direct sun outside? did you just move them outside( cause up until 2 nights ago we were still having some really cold nights)
They were initially started in plug trays and then transplanted to 6 packs which I don't think that they have outgrown. They were shaded at first but have had increased exposure to direct sunlight. They've only been left outdoors on nights where the temp didn't go below the low 40's.
I used very diluted fish emulsion early on, have not fertilized recently. It is rainbow cascade trailing lobelia. The same thing is happening to african daisies, pansies, snapdragons and several other plant varieties. I am beginning to think that an earlier suggestion about them being exposed to cooler temps could be the problem.
When some plants are stressed because of lack of certain nutrients the leaves will, at times turn red. Early exposure to cold climates shows as translucent spots on the leaves or the leaves will curl and die. This does not always happen but I would feel that you are having a response to nutrient problems.
I hope someone may have more input to your problem but I would lean toward nutrients. One bright spot is the red lobelia foliage makes the plant have a unique look.