FredL

This tree looks healthy as can be to me; I would not be worried about it at all. I think the browning is a temporary effect of your pruning and will soon disappear as new growth overtakes it. You are obviously a close observer of your tree(s) and will soon adjust whatever is causing this very temporary effect as you continue to observe the effects of what you do to your trees.

I apply about a tablespoon of 7-7-7 fertilizer from Walmart to my trees about once a month from about March to about August or September, or something equivalent. During Fall, I switch to a low Nitrogen fertilizer. They are all growing like crazy, so it hasn't seemed to have done any harm yet. Because of the particular soil mix I use, it may not be necessary but I enjoy doing it, so I do.

Fred