Although it may be put forward as a "Joint" IVA, unfortunately they are still treated individualy for the purposes of voting. This means that although you may have had 2 creditors vote, which may have been enough for a yes vote on your IVA, if those creditors did not make up part of the other IVA then effectively there have been no votes on that one.
That is my understanding of it. The insolvency act is a difficult bit of mumbo-jumbo to decipher.
If creditors decide not to vote then nothing can happen. These rules are being changed however and are due to come into effect later next year. It will be more in line with the Trust deed, where by not voting is taken as a yes. Until this happens we are all subject to the increasing unwillingness of creditors to vote/get involved with the IVA process.
Your IP could try and get an answer from a couple more of your creditors, or one of yours and 1 of your husbands. Then you have another factor though which is the potential increased administrative costs of your IP depending on how they are charging.
On the way to a brighter future....

Kind Regards.
Lee