Mobile Open Rates

Over a year ago my mobile open rates were in the 30-40% range.  Toward the end of the year, it started decreasing and now the rate is at 6%.  Why?  That seems unusual.  Is there a problem opening the campaigns on smart phones?  Has something happened with your reporting system?  My total open percentage has actually gone up by 10-20% but Mobile open rates have decreased.  Help!