First, congrats for the tier advancement.
Sadly many CC's have the same problem of participation numbers for many reasons. Best to post this in the CC Corner to get ideas from fellow CC owners.
However it may help to advise players when they join, that they are expected to participate in club activities. Make the comps varied and fun and possibly offer incentives )a cheap sleeve of balls - even the 10cr ones if you can.
As you all have deafness in common, hopefully it will create a strong bond between everyone. Try having a alternate shot comp between you all partnering each other, 2 points for a win and the overall winner is the one with the most points. A/S is a good fun sociable game. Do the same for matchplay if you can organize times. By playing with all members you can stress that you want all players to help make the club better.
Good luck