iphone 5 not synching Outlook 10 calenders

On October 18 all of our iphone 5 models stopped syncing with our Outlook 10 calenders from our microsoft exchange server, before that date we had no issues. They still work fine with iphone 4s and older models.

Some of the phones still show the calenders but with no updates past the 10/18 while others will not even list the calenders on the calander page.

We still each get our own personal calander updates but we can no longer see the schedules of the service techs or add to their calenders.