It doesn’t seem likely that this is caused by the recent updates. I’ve run some tests on your site, both on gtmetrics and tools.pingdom.com it has a great score, 99% on gtmetrix, which is near perfect.
I also tried as a “real user” (me), and found your site responding very fast (from Europe).
I always recommend to use the .htaccess redirect, which results in a slightly faster redirect than the php redirect.
If you want to check what the impact of Really Simple SSL is on your page speed, you can try deactivating the plugin. Please choose “keep https” in the popup. Then test again.
@rogierlankhorst thanks so much for taking the time to answer my questions, testing my site, and for explaining it to me. I’m really glad to hear that my site worked very fast for you! I tried deactivating the plugin with “keep https” earlier this morning and that didn’t affect my speed, so it sounds like the plugin is not the cause of my issues.