Forget the Co2. If you don't do something immediately you will lose all of them one by one. They look like they have been damaged by agar on their leaves.
They are too wet. You should remove all of them from their containers and cut off all the brown parts with a razor. Throw away any weak ones, they will not make it.
Soak them in a half strength systemic fungicide for 10 minutes. The brown parts may not be infected yet but if they aren't, they soon will be.
Place them out on paper and dry completely. 2-3 hours is ok.
Pot them up in a shallow container in bark charcoal perlite mix with large pieces of polystyrene for half the depth on the container. (Use a coarse mix! - No less than 5 or 7mm). No moss.
Mist them with boiled rain water if possible whenever they dry. They should dry out regularly and completely every day. (When I say dry out, I mean all the surface moisture, including the roots) A fan will help this. A fan is essential.
Keep them at 27 degrees during the day and 20 at night. Keep the humidity high but only if there is strong air movement.
Do not feed until you see some actual new root growth. If they survive, this may take 3 months.
Be prepared to loose many of them. Remove them as soon as you notice browning in the centre of the growth.
Good luck!
