Sorry, but the two issues are not at all the same!! Rick, your apple blossoms are just showing some weather damage......nothing to worry about and nothing to treat. Fwiw, a great many early blooming trees and shrubs will produce flowers that show this sort of damage....typically just the result of a heavy rainfall. We see this all the time in our wet PNW springs......and we grow a heck of a lot of apples here in WA state!!

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.

The only information you have given us is 'they are the exact same tree' and that may be true but subtle differences in location can change variables in these cases. A boulevard tree, for instance may get some salt from snow plowing. A tree close to other trees will not get as much sun as others in the open. That's why you might see some trees already past peak with fall colors while others that are the exact same species still have green leaves. This year in my country, color change has been scattered with spotty frost pockets and strong winds. Some years everything seems to change at the same time, some years not so much.

I stop fertilizing when temps rise above 80-85*. High temps make roots and the above ground parts of plants very lethargic when they need water most. How readily water moves into cells depends on the level of solutes within the cell. The higher the level of solutes in the cell, the easier it is for water to pass through the semi-permeable cell membrane and into the cell. Conversely, the lower the level of solutes in the soil solution (free water in soil), the easier the cell solution passes the membrane into the cell. For a high % of terrestrial plants other than cacti, root function begins to drop off at root/soil temps of about 80*. If the pot is shaded, root/soil temps usually lag ambient air temps by 10-15*F due to evaporative cooling, so as long as the soil is moist, air temps in shade would need to be in the mid 90s before there was a serious issue with root function. In full sun pounding the pots, soil temps can be much higher - at least 15* higher than ambient air temps in most cases, though that varies too with soil moisture levels and air movement. High root temps are a stealthy attacker. Most often, you won't even realize the damage done to roots (especially trees) on the sunny side of the pot until late fall or even early spring when branches on what was the sunny side of the tree start dying and root rot becomes an issue to deal with. So to be safe, I stop fertilizing at 80*F which facilitates water uptake and movement in the plant. That is also why I try to use controlled release fertilizers sparingly. Their release rate is driven primarily by temperature, so when temperatures reach the point where you want to pull back on the level of salts in the soil solution, controlled release fertilizers will have rendered the grower with no control other than trying to scrape the fertilizer prills off of the top of the soil. I like and feel as though I need the control over nutrition offered by synthetics like Foliage-Pro 9-3-6 in order to achieve the best results. I do use Osmocote-Plus sparingly for younger plants which need to develop more mass before they are started along the path to becoming a bonsai, but not on the trees which are in the stage where I have started developing finer branching and am reducing leaf size. That and beyond is when control is most important. For other hobby growers not saddled with the concerns that come with bonsai, it's simply trying to make it easier for the plant to get water when it needs it most. Al