39 day old tomato plants, started by seed and still indoors. started with cherokee purple. they are wilting from the bottom up. watering doesn't help. threw one plant away, when half of the plant was wilted...just in case. stem at soil level is darker but wondered if it was characteristic of this plant. stem is not hollow, nothing floated out when soaked in water. i did apply store bought manure mixed with peat and pro mix. placed the mixture on top when transplanted. could this be nitrogen burn. any advise appreciated. not all plants are affected, but i am trying to keep that from happening.