and usually water for several minutes two to three days a week (It’s established)

==>>> in the norm.. you really shouldnt need to water an established tree ... but you note drought ... plus a severe change in its microclimate ... removal of the other tree ... who knows how that changed the near surface roots ability to process water.. plus built up heat form the sun on the soil ....you were spot on with adding the mulch ..

i NEVER fert trees .. besides.. its stressed.. not hungry ...

so all i am left with.. is to take a hand trowel.. and dig a few 3 to 6 inch holes around it.. and FIND OUT about moisture at depth.. and if its bone dry.. then put a hose on trickle.. and water deeply ... moving the trickle around the tree every so often ...

you left some pruning stubs.. you might want to figure out how to get rid of them ...

ken

https://duckduckgo.com/?t=ffcm&q=pruning+stubs&iax=images&ia=images

Thank you, this is helpful!

I cannot speak to gardening conditions in PA but around here, Japanese maples push growth in summer that looks exactly like that. By trimming when you did, you may have encouraged that growth. It's frustrating because the growth is unattractive and almost always comes in whip-like branches that shoot out from the crown. I generally just cut them off.