It's very likely due to the domain switch but to give yourself something else to do to do besides what you've done so far (and if you haven't done this already) and give yourself some direction to take while you're waiting for your rankings to come back up, go ahead and isolate how the drops in traffic are occurring:
- Research what keywords mapped to which of your old landing pages and which of those keywords are now bringing in less traffic.
- Did you completely fall out of the results for some of your keywords or have you just dropped somewhat in the rankings for all of your keywords?
- Are you now only ranking for brand terms?
- What specifically has changed with your traffic
At this time, you may do well by coming up with a strong content strategy and working the PR and G+ channels to get that content out to new and existing audience members--it can only help.