Oncidium Potting Query-Overgrown or Ok?

[shoebee]

Hey there.
I was at a yard sale today and the gal was selling her Dancing Lady Oncidiums. They're currently in pots without drainage ( I think they came that way) and are set in Perlite with just a layer of stones on top. The tag on them suggests repotting in the spring but we're past that now and well into summer. I can see that the lowest bulbs roots seem to be not at their best. Wondering if I should split the long rooted sections off and gently try to pot them on their own? Or should I repot the whole thing as it is in new perlite or try a bark/charcoal mix?
I'm in a climate that is very dry in winter so I worry about those long spreading roots...

I'm not the greatest repotter in the world so all and any
advice would be most welcome.
Cheers~
shoebee

PS. These orchids came with tags that tell you how much they should weigh when watered. Even when I bought fancy orchids at a specialty orchid greenhouse I never got that info. Weighing your orchid is new to me!