Don’t update XStore core plugin without theme update! Always check the required theme version for the XStore core version http://prntscr.com/pfwyqdhttps://xstore.8theme.com/update-history/
Now you need either downgrade the core plugin version to one that is compatible with your theme version or update theme to latest version 6.1.2. What do you prefer?
If you want we can help you with theme update (it’s free service).
I have re-added images using optimized jpg versions (20KB) instead of the png versions (100KB), cleared cache and everything works fine. Seems problem was related just to cache.
Why do you use png images if bg is not transparent? Png format increases the size for the colorful images and large images -> large page -> slow site.