My second plant doesn't seem happy.

To me she looks thirsty. Every plant is an individual with different requirements and what is OK with one may not be what is right for any other. Try giving a deep watering to run off and I would be surprised if she did not pick up. Also, at this age and size, plants need surprisingly little feeding and it is very easy to burn baby plants with too much/too strong feeding, while they are still babies. Quarter strength every 7-10 days at this size should be plenty. Plants this size do have surprisingly long roots already, and unless you are deep watering to ensure your substrate is moist all the way through from top to bottom, this too can lead to droopy plants. Have a look at my diary "Holy Mackerel" to see the root system of a 3 week old seedling and this may give you an idea as to why it is so important to make sure the substrate is moist all the way through. Your plants roots will not explore/grow in dry soil, nor are nutrients available either. Hope this helps,.... Organoman.