Phal: Great roots, bad leaves. To fertilize or not to fertilize?

[CarrieCanary]

I am rehabbing two phalaenopsis NoID orchids that I left with my family over the summer. What I think happened was they got sunburn and my mother decided it looked like bacterial leaf spot and cut all but one or two leaves off. The roots look phenomenal though. Nice new growth and everything. I was growing them in a 1:1 sphag/bark mix in a well-aerated (by my dremel tool) plastic pot.

I know you're not generally supposed to fertilize plants with bad roots, but since I have the opposite problem I was wondering if giving it some fertilizer would help grow it some new leaves? If so, what's a good proportion/schedule?

preemptive thanks for your help!