WordPress constantly hitting Virtual Memory Usage limit

My website https://www.thetinyhouse.net has been constantly hitting the PHP memory limit for my web host and I’m not sure why or what to do about it. It doesn’t appear to be affecting front end users (at least not that I’ve been able to tell), but I am concerned that it is somehow limiting performance, and I have had issues while working in the dashboard with pages not loading or just loading to a white screen.

The memory limit is 1.5GB, and I am frequently running at 1.45 or just maxing out at 1.5. Perhaps this is just normal for a site that gets the traffic that I’m getting?

About the site:
-It receives about 50,000 visitors per month, with 20-30 users online at a time usually
-I use ZenCache Pro as my caching plugin
-I just implemented a static CDN (today), but have not seen any reduction in memory use

What I’ve tried:
-I’ve tried disabling many plugins but have not been able to find any one that significantly impacts anything
-I’ve tried using the Plugin Profiler to remove plugins that are using a lot of resources
-I’ve installed WP-Memory-Usage which shows WordPress using about 41MB.

How can I really figure out what’s causing this? Do I just need more memory?