Those trees are pretty fast growers and most will probably not fertilize them at all, but if you're wanting to push them then by all means throw some fert down. You can go with a fast-release 10-10-10 or 13-13-13 for the fall feeding, about a solo-cup's worth per tree. In the springtime you'd be better served with a coated fertilizer (my local SiteOne sells a Triple-19 as a coated L&O fertilizer). That's what most of the landscape companies use to fertilize trees & shrubs during the growing season around here. Don't overthink it, these things are resilient and will grow without any extra fertilizer. You adding some is just going to further add nutrition to the soil for them to feed from.

 

Great, thank you!