http://www.swtor.com/support/helpcenter/6856
For further help on that;
"
The most important thing for you to be aware of as a guild leader is that only Subscribers may be guild leaders of Subscriber Guilds in Star Wars™: The Old Republic™. If you plan to become a Free-to-Play player, you should prepare your guild for the transition by passing your leadership on to a guild member that plans to remain a Subscriber.
If you do not do this prior to your account status changing, the system will automatically pass guild leadership on to the highest ranked active Subscriber in your guild once your account changes to Free-to-Play. You will remain a member of your guild and will have Free-to-Play access to guild features. "
If they are logging in and you are doing the same, you should see leadership pass prior to that 30 days if they are F2P (unless they are also a subscriber, and are logging into that character).
Worth noting for the future as well once/if you get guild leadership back that the system is apparently set up to pass leadership to the next up subscriber, so if you and your partner are dropping subscription, you will want to prepare for that with the guild.