Butterfly2014, when our case officer contacted us in Feb, one of the documents requested was an AFP Police clearance, as my husband had now been in Australia longer than 12 months (we had gotten a new Police Check from Norway in October as we knew it was close to 12 months old), so that might be something to think about - although your case officer will request it if they want it (we didn't even know we had a case officer before this request).
You will normally have 28 days to provide the additional information requested.
No idea about the Health Check though - hopefully the case officer will take the processing time into consideration and you won't need a new one - but can't say that for sure, as my husband held off on his medical so as not to run into this situation.