Looks like majority of the leaves are fine, kinda hard to tell from the pictures. I wouldn't worry too much, shipping is stressful to the trees. Don't leave them in the medium from the nursery too long.

Everything I see looks to be very normal.

why would you think you were sold a plant that needed to be sprayed for some disease??? .. thats bordering on loving it to death ...

it stressed.. for shipping from grower to seller.. to your house...

how cold was it outside when you brought it home .. could there have been cold damage ...

light from a skylight will not be sufficient long term ... but thats not apparent now ...

it might also be stressed from temps in your home.. but it will get over that.. once its acclimated to such ... its not too cold.. but it might not be what its used to at the growers ..

water properly ... let it near dry between deep watering .. insert finger and water when it needs water ... surface of the media is irrelevant. ..

and try not to love it to death ...

ken

ps: its stressed.. and fert is not a response to such...

Was recently shopping in nursery in Ontario (not a box store). They had a truckload of large citrus trees that just arrived from Florida. They were $399 and $799 for 10 and 20 gallon trees. Unfortunately they were covered in red citrus mites. They were easy to spot. I took a magnified picture of the mites with my iPhone and showed the owner. He said they just arrived from Florida and they had not got around to spraying them for mites yet. In theory they should have been sprayed in Florida already for mites but that is not always the case.

The first two pictures of a lemon tree could show salt build up or sunburn.

Third picture shows a sticky honeydew substance on the leaf. This is a signal that something is piercing or sucking the leaf. Could be scale or spider mites. Look on the underside of leaves. Spider mites you might see with naked eye but easier to see with a magnifying glass. Mealy bugs are easy to spot. Regarding the shape, it could be mechanical damage. When the leave grows it will grow around the damaged which distorts the shape.

Overall your trees look in pretty good shape. The low humidity indoors is extremely hard. Moving them outdoors in the spring will help. Spider mites thrive in low humidity. Mealy bugs thrive in high humidity.

Skylight won't be enough year round. They will need to go outdoors and you will need a grow tent with LED or something else for 8 months. A typical skylight will help but not enough light to sustain the plant.

So did anything that lemon have to offer help too? How's an update sound to you? I would love to see one)