Try and distinguish between the new growth and the oldest leaves, especially on artichokes. As long as the rhizomes stay healthy, the leaves & fruit will eventually come, no matter how ratty any one leaf looks. Transplant shock can be rough and produce stress signs in all plants, but it's best to wait it out a bit and see if the new growth recovers. Splashing soil up on the leaves while watering can produce yellow & black spotting too, it's one of my biggest challenges, as a moment of garden ADHD while watering means I've just splattered an entire row of seedlings with soilborne fungi and bacteria. It's often localized and never spreads beyond the affected leaf, except on my solanums (tomato, eggplant, potatoes, ...) it can mean I've just sent early blight everywhere, as I can't seem to get that disease out of my garden ever since my Home Depot tomatoes were infested. Whiteflies leaving your nursery-bought plants is a huge problem, it's illegal for the nursery to sell you infested plants. Get a refund and/or find another nursery. I rarely use box stores anymore, their pest prevention is weak (at best).

Fungal disease of some kind. How often do you water and for how long? How much rain have you gotten? Are you down in a low area or has that area been covered with brush or something? It looks like it was smothered or otherwise protected from sun and wind for a time. I take an organic approach to lawn fungal diseases. I use ordinary corn meal at a rate of 20 pounds per 1,000 square feet. Corn meal attracts another fungus which is predatory on the fungus causing your disease. That fungus is called trichoderma (try ko DER mah). It takes 3 full weeks before you see any improvement. That can be the longest 3 weeks of your life, but after that you should see less yellow and much more deep green. Corn meal is also an organic fertilizer so the dark green color will be very noticeable at the 3 week point. If you have used a chemical fungicide recently, then the corn meal will not work against the disease but it will definitely green up the grass. And yes this is the same corn meal you cook with. You can get it in 50-pound bags at the feed store. And no, it will not attract varmints. Seems like it would but it does not. It does seem to attract birds but they don't eat it. They just come and visit. You can apply corn meal any day of the year, rain or shine, or every day of the year, without fear of hurting anything. If you wan to take a chemical approach, I cannot help you. Our temperatures, humidity, and rainfall are usually outside the recommendations on most chemical fungicides. I gave up on them years ago when I found out how well corn meal works. On another issue you did not ask about: You are mowing your St Augustine much too low. Raise your mower all the way to the highest setting. It will take a month or so before all the grass gets tall enough to be mowed but it eventually will. Mowing it low favors the bermuda which is mixed in with it. Mowing it high can have the effect of choking out the bermuda. Tall St Augustine looks very lush.

No fungus gnats won't cause this kind of damage. I don't believe it's a disease or soil related either. It looks typical of the damage caused by chafing/rasping insects. The 'spots' start out light or clear because the tissue containing the chlorophyll is damaged. It turns brown upon tissue death.

It is normal for citrus to drop older leaves, especially on established trees like this one. And it's always a good idea to fertilize regularly. But on the third leaf from the right, I think I see Whitefly larvae and their white stuff they leave around them. And I think the first two leaves may have a little bit of sooty mold, which would come from the Whitefly larvae droppings, a sweet sticky substance. It looks like a pretty mild case. On a tree that size they won't really damage it, it's more of a nuisance then. But if I were you I'd take the hose with a spray end and give it a good hard wash with water, especially on the under sides of the leaves. That will get rid of a large percent of them, then I'd do that every week for a while, say a month or so. That will help get rid of new ones as eggs left behind, hatch out. Overall though, johnmerr and pip are right, it's in pretty good shape, just need some food.