Research ethics committees often ask for more information - for example, about how you will handle certain situations or potential problems. Much of ethics is about trying to anticipate the unexpected - thinking about what could happen in your research, and how you will deal with it if it does.
It may be that from the committee’s experience of reading other applications, they have ideas about what could come up that you have not thought about. Sometimes applications tend to address the most obvious or sensitive ethics questions (such as consent) but don’t pay enough attention to less obvious issues (e.g. researcher safety).
Perhaps the committee has noticed something that you have missed, or there is something they would like you to clarify, or something that you did not see as being sufficiently important or relevant to include in your application. In such cases it is almost always easier to provide the information that the committee has asked for, in order to move on with your research. However, it is important to do this thoroughly - use the information elsewhere in this guidebook to help prepare your response - in order to reduce the likelihood that the committee will come back to you for more information.