line spacing between paragraphs disappeared from all blog posts

The line spaces between paragraphs on every blog post I had done disappeared a few days ago. Up until then, the layout was good. Line spacing between paragraphs were there in the draft and there when I published.
I am using www.ads-software.com twenty twelve, website https://www.sacristies-of-the-world.com

I was asked if I was using the Visual or Text editor and told not to switch between them. I was also told to try deactivating all plugins to see if any of them were causing the problem.

I answered:-
“All my posts have been written in Visual editor. But thanks for the tip. I won’t be tempted to switch between Visual and Text editor.

I deactivated all my plugins. I don’t have many. And the line spacing came back. So I activated them all except for the most recent one “WP AMaSIN – The Amazon Affiliate Shop” and the line spacing was still there. So that’s the one that has caused the line spacing problem.

So where to now? How can I get round the line spacing problem with WP AMaSIN? Thanks.”

I can only reinstall AMaSIN if the line spacing problem can be overcome.
There is a bigger problem too, relating to the Associate Tag, API Key and Secret Key. I can’t find them. I looked through all the www.ads-software.com plugins relating to the Amazon Affiliate programme. I chose AMaSIN because it looked the best one to me. So I am happy to persevere. I will put it in a separate post on this sub-forum. I’m not sure if that’s the right way to go … Thanks.

https://www.ads-software.com/extend/plugins/wp-amasin-the-amazon-affiliate-shop/