Pictures please. I am assuming that the tree and not the pot is 16 inches tall but not sure. If the pot is 16 inches tall, how big is the tree. or how big is the pot for that 16 inch tree.

A few close ups of the leaves would be helpful. It’s hard to see if there’s a deficiency with the lighting.

The first thing everyone is going to tell you is to loosen that stake.

Do you plan on putting the tree outside during the growing season? That will surely help.

Always check your soil when you have a citrus problem. Is it soggy? How long does it take to dry out a few inches down? What is it planted in? Are there enough (or any) drainage holes in the bottom? Do you fertilize?

Don’t be afraid to pull the whole rootball out and check to see if the bottom of the pot is wet or if the roots look healthy.

Most common citrus problems are overwatering/soggy soil leading to root rot, insect damage, nutrient deficiency. People here are really helpful about figuring out which one is the issue.