Crystal Reports Subreport Linking using parameters

Message

   Hi,

I have used a SQL command in my main report, which uses parameters as below

where rg.resourcegroupid ={?team} AND c.startdatetime >= cast({?start} as datetime) AND c.startdatetime < cast({?end} +1 as datetime)

I have 4 further subreports linked to the main report, they all use the same paramaters as above.

As individual reports they all run in seconds, but when I link them by the parameters below, the report inevitably takes 20 minutes plus to run or sometimes times out.

{?team}

{?start}

{?end}

Any ideas on how to make the report run quicker?

Thanks