I have just upgraded my Lightroom software from version Lightroom 4.1 to the latest version (Lightroom 6.1). I have installed Lightroom 6.1 in the very same computer environment as the previous version (CPU INTEL i5 @2.67GHz RAM 8Gb 64bit, the OS is installed on a separate SSD with about 80Gb of free space. The catalog is on the SSD). I have also installed the online latest available upgrade. Yet I notice that the new version (Lightroom 6.1) performs MUCH slower than the previous one. Why??