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They sell citrus specific fertilizers, if you want to go that route. This article also has information about what lemon trees need:
https://www.gardeningknowhow.com/edible/fruits/lemons/learn-about-fertilizer-for-a-lemon-tree.htm

I would not adjust the micro nutrients (such as zinc) or the pH (with the lime) unless you have had a soil test done. Many local extension offices will do soil tests for a small fee. Or you can send a soil sample to UMass Extension and they will do a soil test for you. Here is information on doing that:
http://www.umass.edu/soiltest/index.htm

Sounds like your lemon may be suffering from insufficient humidity and is much too dry. Make sure that it is receiving adequate water and increase humidity if possible. Lemon trees require deep watering once weekly and more when they're in containers. You may also want to give it some fertilizer. Insects can also affect lemon trees. Here is an article or two that you may find helpful: https://www.gardeningknowhow.com/edible/fruits/lemons/learn-about-fertilizer-for-a-lemon-tree.htm
https://www.gardeningknowhow.com/edible/fruits/citrus/leaves-falling-off-citrus-tree.htm
https://www.gardeningknowhow.com/edible/fruits/lemons/growing-lemon-trees-containers.htm

Make a cut into the root and paint the fresh cut with undiluted Round-up. The fresh cut will cause the plant to pull the Round-up into its system and will kill it. You may need to repeat 2-3 times if the roots grow deep, but it will work.

Have you fertilized? Nitrogen encourages leaves to grow, but not fruit. Too much can actually keep a plant from producing fruit. This article has information on how to fertilize your trees: https://www.gardeningknowhow.com/edible/fruits/citrus/fertilizing-citrus-trees-best-practices-for-citrus-fertilizing.htm

I would also try giving them some phosphorus rich fertilizer, like bone meal. If they are lacking phosphorus, the trees will not be able to produce blossoms (which means no fruit).

The requirements for lemons are very similar to that of limes. If you have not read it yet, this article may also be helpful: https://www.gardeningknowhow.com/edible/fruits/lime/reasons-and-fixes-for-lime-tree-not-producing-blossoms-or-fruit.htm

Here is an article that you may find helpful: https://www.gardeningknowhow.com/edible/fruits/lemons/growing-lemon-trees-containers.htm

I copied this answer from another source but thought it would be helpful to you.

Citrus only changes color in cool/cold weather. Since you move yours inside in winter, the fruit doesn't change color. Of course you can't leave it outside in winter. You just have to accept that the fruit won't change color. That doesn't mean it isn't ripe. So try some of the older fruit. A lemon is ripe when it's big enough.

My citrus is in a greenhouse that is only heated enough to avoid freezing. The fruit starts to change color in Oct/Nov as the nights fall into the 40s and 50s. They fully color up with lows in the 30s. If you get your tree that cool in winter the fruit should turn yellow. But it's not necessary for useable fruit.