If the website is the one as your username, then I could see from the source that your website have "Twitter Cards Meta" properly setup, and Meta tags are correct.
Twitter released this new preview tool, which still a bit buggy. And when you are getting "Timeout. Exceeds 3 seconds fetching this page." means your site responding a bit slow. You have a graphics heavy website. So maybe that could be a reason.
In other words, it does not seems to be a plugin issue. If you take a look at your page source, you will see perfect valid meta. So, if you even added the meta by hard coding or used any other plugin it would not have made any difference. And this is a very basic plugin, it could not be responsible for making your site slow.
As a suggestion you should use some Caching plugin to make your site faster. You could also consider using free service like "CloudFlare" to serve your site faster.