I don't think that's dry droop. Maybe it was before you watered, but that looks more like over watering, which is also a sign of RO use. I never see it spoke about, but have done enough trials to recognise it.
I always add a token amount of feed to RO water. Others mix some tap water. You could think about cal/mag if you have spotting (I missed that)
If you have been really dry, it may of effected your potting mix. A few days being damp might be needed before it comes good again. The calcium is there. I just think it was in a dry form, and your plants sucked up clean water almost uncontrollably. I don't really know the mechanisms at play, but the result is familiar.
Watering correctly should fix it. Not overnight, but soon enough. Stop using neat RO and give them a damn good wet. Wait half hour so your absolutely sure it's all soaked through. Then water till run-off again. Cal/mag this once is your call. I would wait to see if the substrate can provide it, before adding more than might be too much long term