Help to Customize 4 Column Pricing Layout

Site URL: https://ray-cone-ap64.squarespace.com/home/headshots

Hi.  I have done some custom css for my 4 column pricing layout. I initially worked on the code in  

design - custom css 

so I could view the changes live. That made the affected entire site.

then I tried 

settings - advanced - code injection - header (with and without <script>)

also altered the entire site 

I have tried "code" (from the droplets but some tricks this old dog hasn't got the handle of yet.)

I have downloaded Google Chrome Extension --- Squarespace Collection Block Identifier --- but the id= I haven't got the hang of as yet (it has #block-yui....... not id=) like I have seen on others sites .

please help ... this is doing my head in.

*note: I have placed the code I created back at the very bottom in 

design - custom css 

incase one of you wizards and your dark magic can figure out what I need to do 

Thanks

fixed. thank you very much @tuanphan