Dwarf Meyer lemon tree with lightly mottled leaves

Hi! I have a dwarf improved Meyer lemon tree, about 3 ft. tall, which I acquired in December--never grown one before. It lives inside under a gro-light in my kitchen. The air is somewhat dry because of our house-heat. I haven't fertilized it yet, since this is a dormant period for citrus (?) The leaves are beginning to appear lightly mottled (see photo). It hasn't dropped many leaves, and it has lots of blossoms on it, but I don't like the mottling. I don't see scale or other pests. Is this mottling happening because it needs fertilizer? If so, what sort is best? Should I do a foliar feed?
AS you can see, I'm a beginner at this.
Thanks!

. . . . here's the tree itself.

I would take a peek at the underside of the leaves for spider mites--they will be very tiny and hard to see, unless you have a magnifying glass they will look like tiny reddish-brown or brown dots. They love warm dry air so they're common on indoor plants in the wintertime. The telltale sign of a spider mite infestation is a stippled pattern on the leaves, and if the infestation is bad enough sometimes you'll see some webbing as well.

If you do think it's the SM's, I would take the plant outside if you can, or else into the sink or shower and give it a good bath/hosing off, making sure to clean off the undersides of the leaves. Then once it's dried off, hit the undersides of the leaves with neem or insecticidal soap or your pesticide of choice (as long as it lists spider mites on the label). You'll probably need to repeat this treatment a few times over the next several weeks to fully control the problem. If there are any other plants near your lemon I would do the same bath/spray treatment for them, I can almost guarantee the mites are already on them even if you're not seeing symptoms yet, so it's best to be proactive and stay one step ahead of them.

And be aware that leaves that have been significantly damaged by the mites may start to turn brown and eventually die and fall off long after you've gotten rid of the spider mites, so don't be alarmed if you get rid of the mites but then the leaves seem to get worse and eventually die--it's just because they were already damaged before you killed the mites. If that happens the tree should put out new leaves to replace the ones it loses.

If it is blooming, it will need fertilizer. Maybe 1/2 strength. Do it a week or so after you do the first round of cleaning that ecrane outlined.

Thank you, ecrane and juneybug. I looked under the affected leaves, and yes, little brown dots. Not a huge number, thank heavens, but enough to tell me that I have a problem.
I'm going to do the bath-treatment, and spray with Neem. . . and then, apply a low-dose fertilizer.
And check the bougainvilla that lives next to my Meyer for mites as well.
Thank you both! I appreciate your halp so much.

I wouldn't fertilize until you've got the spider mites under control--it's generally not a good idea to fertilize plants that are under stress, and from what I can tell the symptoms you're seeing are caused by spider mites not a nutritional deficiency. Good idea to check the bougie for mites too, but even if you don't see any mites I would give it a bath and a spray with neem too...judging by the amount of leaf damage I see on the lemon, I can almost guarantee any plant sitting next to it is going to have some mites on it too, and unless those are the only two plants in the area you're much better off getting ahead of the game and proactively treating the bougie. Otherwise by the time you realize the bougie did have them after all, they'll already be on the plant next to it, etc.

citrus trees don't go dormant. if you feed when there are flowers present, it may very well drop the flowers but on the other hand, if you feed when very small fruit is present, it can often drop the fruit (known as blasting). so either way you go, take it easy on the feeding.

Good advice about the feeding. I will hold off on fertilizer--are you saying that I should wait until the leaves look "normal," e.g. dark green and healthy, before adding any ferts (either soil-drench or foliar?) Or just wait a while till spring has sprung?
I do appreciate the help. And my Meyer does, too.

Those leaves are never going to get dark green and healthy--the mites have damaged them and you can't undo the damage to the individual leaves. What I've typically seen happen with my plants is that many of the damaged leaves will eventually die and fall off, but they'll be replaced by new ones. I usually wait until I'm sure the mites are gone and the plant starts to put out new growth or replace the dead leaves before I'll fertilize, but you'll also need to pay attention to when is the right time to fertilize citrus.

what ecrane said. go to lowes and buy a good quality citrus feed. a very small bag should suffice because you don't want to over do granular feed on a potted plant.

Thanks, all. Today my Meyer's lemon AND my Bougainvilla went (separately) into my tub for a wash-off with the flexible shower-head. Then (after drying) the leaves were sprayed with Neem. When they came downstairs again both looked rejuvenated from their shower. I should probably do this with all my houseplants. . . the sight of me hoisting the plants up and down the stairs was probably a bit hilarious. . .
I really appreciate the precision of your answers as to when and how to fertilize. What I've read suggests that the important time to fertilize is just when new growth begins in the spring. Some folks use a diluted fert during the winter, or one lower in nitrogen. I don't know enough about that however.
Anyway, I'm happy that I have a chance to save my citrus, which is a lovely plant to have inside in the wintertime with its scented blossoms. Thanks!

don't be discouraged if all the leaves fall now. sometimes it just happens and especially if they have been under stress but new growth won't be far behind. my experience with citrus is all with in-ground trees so you will have to learn, kind of trial and error, what type of feeding schedule will work best for you. an interesting side-note is that the correct pronounciation for citrus is ki-trus.....i try to use correct names whenever possible but if i called them kitrus around here, people would think i was from another planet! lol