Problem size resize image after migration server

[ingrossoerisparmio]

Hi guys,

 

Some days ago I switched from a shared hosting to a VPS.

 

I've noticed that after migration when loading images in product data sheets, 800x800 images (thickbox_default) are heavier than before (twice the size).

 

The settings in the preferences / images are the same (quality 90 jpg, png quality 7).

 

In fact, now the statistics with Google Page Speed Insights show me a problem "resize image" indicating that the images can be reduced by 40%.

 

How is possible that the uploaded images after migration are much heavier than before? I have to install some module on apache server? Permission problem? Or?

 

Thanks in advance.