S/H transition w/o new root growth - thoughts?

[arianeos]

Hey everyone. I have 7 oncidium alliance plants new to my collection (Onc. Sharry Baby, Witch's Jewel, Pacific Passage; Oncsa. Gower Ramsey; Mltnps. Lennart Karl Gottling, Keiko Komoda, Rene Komoda) that look like they might have some insect damage. I haven't found any scale, mealy bugs, thrips, or aphids themselves but the damage is visible in a few small places.

All of these plants just went out of bloom and have dried out their flower spikes, but they don't show any new growths let alone new roots yet. Due to the possible insect damage and not wanting to introduce anything to the rest of my collection, I want to repot to get rid of anything that might be hiding in the old medium and clear the issue up faster.

That being said, I know switching them to s/h without new root growth could be a death sentence since they're a little under the weather. Has anyone here had experience just potting them up into the leca pellets & s/h pot but then draining out the reservoir after flushing? I'm considering doing that to use the leca as an inorganic medium and then only leaving the reservoir full once there's new growths and new roots, but I figured I'd check on here to see if anyone else has tried this before. I've only ever used leca with s/h, not as an inorganic medium entirely on its own.

Thanks in advance for your help!