Sudden big drop of image quality in sliders

Hi !

First, thanks for your great plugin !

Then, my problem…
My website has been online for a few months and the picture quality was very good. (Jpeg compressed for web in Photoshop in 1800x1200px and 72dpi, artifact-free, etc, and around 180ko per images).

Today, I just noticed that their quality has become very very bad, perhaps because of last update ?

My website is built with the SiteOrigin builder. The background images in rows are still good in contrary to the SiteOrigin Slider widget I use everywhere…

Those images still appear perfect when I look them in the media library of wordpress that’s why I thought the problem could be in wordpress or in the slider widget.

So I modified the wordpress image compression from 90% to 100% and clearing the cache of the website but it didn’t improved the bad quality of thoses images…

Do you have an idea to resolve this problem ?

Thank you !