Answer: Several things could be at play here. The light, temperature and humidity indoors may not be quite right for your new little tree. Citrus likes moist but not soggy wet soil, high humidty (try misting whatever leaves are left) and they like warm temperatures. Keep them out of drafts and away from heat registers. Overfertilization can burn the roots and cause leaf drop. When you fertilize containerized plants it's easy to over-do. I use liquid fertilizer such as Miracle-Gro and dilute it to half-strength and feed every 3-4 weeks. This provides a constant supply of nutrients without burning the roots.
Root problems are a more likely cause. Root rot infection, physical damage to roots, drought and overwatering (soggy, waterlogged soil) can all cause leaves to turn yellow and fall. It can also cause blossom and early fruit drop. Try to determine which of the cultural problems listed above may be the cause and take steps to alleviate it.
In general, make sure your citrus tree gets plenty of sunlight, and a regular fertilizer program.
Flattend branches can indicate a viral infection or they may just be the result of cultural problems. There's something called "stubborn disease" that results in flattened branches as they develop in the canopy of the tree. This usually results in lower yield, but won't kill the tree. Hope this information helps you nurse your tree back to good health.
Best wishes with your new tree!
Q&A Library Searching Tips