Could you upload your pictures to Photobucket or something like that? Then post those and your issues on the Tropical Fruit forum. There are plenty of FL folks there growing mangos. Without the pics and more detailed description, just impossible to diagnose.

More water. It's still living on the pot roots system..and the ground is wicking away the water. You're in a dry hot climate..water -build a well around it,and keep it mulched on planting is the no.1 priority. Your are correct also that Mangoes sold often don't have root balls knitted together yet and I know some people have had the whole ball of soil fall apart when slid out of the pot. THAT is a major setback.

You always need to be more careful with moisture retaining soils. Large Mangos are quite tough plants and will often come back from severe reversals. Smaller trees are more sensitive. They've evolved in a monsoonal climate where they often get flooded out during the wet season and are completely dry in the dry season. The dry season coincides with the coolest night time temperatures. A wooden skewer or chop stick pushed into the soil to see if there's moisture below is a common method for checking. The surface soil will often look dry when below it isn't. The leaves in your second photo are okay, but don't let them get to the stage of those in the first photo. And keep them away from cold night temperatures.

What you did was tantamount to bringing a bunch of human babies into your home and immediately stuffing them with a huge gourmet dinner and a few bottles of wine. No wonder they're sick. The best you can do for the time being is to flush the soil with water and cross your fingers. Also try to put them in a position as similar as possible to where they came from as regards light, humidity and temperature. I doubt that is your kitchen table, unless they are only there for the photo.