Thumbnails very soft / blown up. Also distorted/stretched

All the thumbnails on this page when displayed on a monitor are 5 across yet they are displaying in two different ways. Why are they doing this please? Why do the thumbnails look very soft / blown up. Why are the images distorted/stretched?

On an iPhone the larger thumbnails display as two across then the smaller thumbnails are three across

1) Larger image – VERY soft/blown up. Very distorted.
2) Smaller images – Look better than number 1. Don’t look all that soft/blown up, but still look distorted

Monitor image https://prnt.sc/qafi2m
iPhone image https://prnt.sc/qafid4
My settings https://prnt.sc/qafj6a

The page I need help with: [log in to see the link]