The members are finding it hard to see the end of one post and the start of another as I said earlier they are nearly all OAP's a lot are visually impaired so I try to make the forum as easy to read as possible for them.
For posts, I like to only have 1 border. On your forum, you both have a border-top and a border-bottom. You can style the posts like this so they would easily know what's part of the post and what's not:
Have you considered buying a theme? A cheap but extremely aesthetic would be Flat Awesome+ from PixelExit by @Russ & @Steve F. You get S-Class support too.