i haven't been taking summer cuttings, but if i was going to, I'd take them when you see the leaves are done hardening off.
as far as fertilization, im still using up a bag of peter's professional 20/20/20 i bought years ago.
in spring as new growth is hardening off i use Real Growers Recharge microbes/kelp/acids mix at 2 grams per gallon once a month till leaf fall.
last year i fed the peter's at 2g almost every week.
when i see the trees are going into storage mode, i use Jack's Hydro 0/12/26 at 2g.
when I'm through with the peter's I'll be using a combo of calcium nitrate and jacks 0/12/26 at around 1:2 grams. maybe 2:3