Great tips--these trees seem to hate any fertilizer, even fish emulsion. I had the same issue where the leaves turned brown and dropped after just a little fertilizer. They also desiccate from wind easily. If my tree comes back, I'll use worm castings and leaf mulch.
There was a video posted by the University of Florida 13 years ago, apparently you are supposed to fertilize with low nitrogen fert with high potassium. Hopefully this helps.
That sucks over here in Sacramento. It gets up to 100 someday each summer. And the guy is saying that it likes it at 70 and 80 in the summer not getting that then
According to Google they do. I don’t have a lot of experience with lychee yet so can’t really give you advices. It could take some time for it to acclimate since yours is only 2 ft tall atm.