I would really
not suggest fertilizing it.
If it's not growing, there's a REASON. It's unlikely that your existing soil has insufficient nutrients but if that SHOULD be the case then the trees are doomed anyhow so no point in prolonging the agony
Infinitely more likely that they are simply not yet established enough in their roots to be read/able to grow. Did you unwind and gently disentangle the roots as much as possible from the rootball when planting? That helps a lot, and in some cases is the difference between survival and death (don't try to go back and change anything now though).
Just make sure the trees are kept evenly, correctly watered (never let them go dry, but never make them soggy either) and give them til next year. They will likely come around before then.
The problem with fertilizing before roots are established is that it's easy to accidentally burn the roots that way and make it even harder for them to establish.
If you just feel like you can't stand to do nothing, use something with a low first number in comparison to the other two numbers, and apply at drastically reduced strength. Absolutely DO NOT use chicken manure, especially not fresh.
Good luck, have fun,
Pat