This had nothing to do with your light and it is 1000% a soil/pH issue. The reason that they have perked up is not due to light, it is because of the soil that you planted them in outside has been acclimated/amended by nature and has had time to "settle" if you will. More specifically I believe that the pH is much more stable in the bed you planted them in because as you said it is "used" soil which is actually better if you ask me. If you were to take some of your soil from outside and use it inside you would see them perk up as well, I believe. I am about 90% sure this is your issue, oh and you need to get a pH meter or litmus paper at the least to test your pH it is critically important to know what your pH is. One other thing is you said you are using organic ferts just make sure your water doesn't have any chlorine in it or it will kill all of your microbial good stuff in your soil. Hope this helps, if you have any more questions feel free to ask
Thanks
@StarBright for letting me know about this thread you are such a sweetheart!