Answer: Yes, I think it is. Some are born sloppy, some achieve sloppiness and some have sloppiness thrust upon them! You are in the middle category and yes, as chair, you must take some responsibility (a good head could also help). Maybe you yourself have run out of steam and should try to find a successor. But on the likely assumption that there isn't anyone in the wings, you may have to sharpen the others up before they are ready for that.
You may have had a considerable turnover of members during the period you are talking about. I suspect that you have just let newcomers pick things up as they go along and, if longer-serving governors have also lost their edge, what they pick up will also get less and less focused and the pressure of a hard-working culture will ease.
You must talk about and organise the induction process which, like everything else, needs to be planned, with people given clear responsibilities for welcoming, informing, accompanying, and mentoring. Newcomers also need to be introduced gradually to clear personal roles and given more responsibility within a year. Meanwhile, you may be able to ask your LEA training team for an in-house session on roles, responsibilities and teamwork. You might buy a few basic books to lend on request. Some of you should meet during the school holiday to review the situation, so that you don't forget how you feel right now and lose the chance of a fresh start.
As I often say, the first meeting of the year is an opportunity to identify where you may have slipped back, without having to put name tags on it, to leave bad practices behind, and to be specific about the good habits which together constitute a healthy governor culture: habits based on corporate loyalty, equality of status and input for all members, and a firm framework for keeping on top of the work and updating knowledge, policies and responsibilities.
An agenda item "How we work together" for that meeting is essential in a case like yours. In particular, you should cover individual roles, induction, and participation in training. You need a system for every member to spend time in school, with a reiteration of ground rules for visits, and some system for ensuring that you regularly review existing policies.
Reminders about the openness of most governors' business and the right of all governors to participate should be combined with a warning about using with discretion any sensitive information about individuals gained through being a governor. Encourage your head to include information about forthcoming issues and events in his or her report to you so that you can take responsibility for planning.