I don't grow citrus in pots, so I haven't had to troubleshoot an associated problem. That said, since your post is about to fall off the top rung, I figured it makes sense to offer my 2 cents. It's almost always more than just one thing that isn't right when problems start happening. Frankly, it's hard to say for certain what is happening without knowing the size of the pots, makeup of the soil, etc. The best citrus resource around is Four Winds Growers. They put their money where their mouth is because their retail sales and risk of potential returns depend on it. I've followed their advice for the most part with my in ground citrus. The answer I offer to you is to align yourself with the Four Winds Growers recommendations: Growing Citrus in Containers. As for fertilizer, I recommend the Miracle-Gro Azalea-Camellia-Rhododendron Food (previously known as Miracid).

Thank you for your reply Patty. I think the sun is fine as this is a south facing window, and the large pot behind it is the mother plant which has been doing great there for years. This picture was taken at dusk, so it looks like a lot less light than they normally receive. I have both potted in standard potting soil. But I think you may be onto something with the fertilizer. I've learned over the years to add a bit extra nitrogen to the mother plant if her leaves started to turn yellow. However, I may have given too much for such a young plant. I have repotted it, and will go easy on the fertilizer and see if that brings the young plant back. Thank you for your help.

Dave you should go to Fruits and orchard to see a couple of pictures. The citrus folks might not be too happy cluttering there space. I got way too many of these tree's, but that is what happens if you get decent in grafting you just can not stop.

Amanda, it looks to me like that tree is a gonner. You’ve put too much stress on an already stressed, under watered, under fed tree. I’m afraid it will see its demise indoors. If it were me, I would take the winter and do some research on root stocks and how they effect the growth habits of the citrus tree you want to grow. Then I’d go to my local nursery like Armstrong’s or wherever you normally go in LA and find a new tree that is grafted to said rootstock that you researched in January and plant said tree in Late January early February into the ground. Late winter early spring is the perfect time of year to plant citrus trees In ground. Then I’d water it consistently and deeply the first year and fertilize it lightly monthly. That’s it. The more care and worry you give to your trees the worse off they end up being from over care. You see, in ground trees are very different than potted trees. They need a lot LESS care, you have to let them do what they’re going to do and address issues only if they arise. Not every tree is going to look perfect or have deep green leaves or bear fruit the first 1-2 years, it takes patience. Rest assured though, you live in LA, it’s basically the perfect climate to grow citrus in so if you have patience and keep an eye on your tree it will reward you with a bounty eventually. Evan