You are indeed in a very strange situation. I'm not sure why your department doesn't get you into a lab. Why isn't this a requirement?

I think every PhD student needs to belong to a lab, have labmates to talk to, and have lab meetings to learn from others who study similar thing. At least you will be publishing papers under your advisors' names. Don't they want to participate a little bit in the research process? To just tell you "work on the topic you want to be known for" is definitely not enough of a mentoring effort. You should talk to your department chair, your dean of graduate school, or anyone who's responsible of getting you to this point. Ask them how you can better your position, how to be more actively involved in a lab. If one of you advisors already have lab space or members you should ask if you can move, visit, join the meeting, collaborate with those people.

In case your major concern is just not being able to find holes to fill. Maybe you can look at previous work of you advisors, pick ones you are interested, give it some thoughts, ask them what are major challenges remained in this area, and how can you solve them. I guess, be more proactive. If they are unable to give you satisfying guidance, move on to other professors in your school. Ask for an appointment and ask them for their guidance. If no one in your department/school has overlapping interest with you, you are in the wrong school. You should use your current credentials (your peer-reviewed work) to transfer to other schools.

Since it's early in your study, you still have time to change advisor or transfer to other departments/school, whatever needed to move you forward.