All of my lightsail hosted wordpres websites became insanely slow, and almost unusable within the last 24-48 hours

Based on your description, there are several potential causes for the sudden slowdown across all your WordPress sites on Lightsail. Since this is affecting multiple sites simultaneously, it's likely a resource or configuration issue rather than a problem with any individual WordPress installation.

Here are some potential causes and solutions:

1. Resource limitations: Your Lightsail instances might be running out of burst capacity. Lightsail instances have baseline performance with the ability to burst above that baseline for periods of high activity. If you've been experiencing higher traffic or resource usage, your instances may have depleted their burst capacity and are now operating at baseline performance only. Check your instance metrics for CPU utilization and burst capacity.

2. Memory issues: WordPress sites can be memory-intensive, especially with multiple plugins active. If your sites are running low on available RAM, this can cause significant slowdowns. The admin area is particularly resource-intensive and would show problems first.

3. Database performance: If your WordPress database has grown significantly or needs optimization, queries can become slow, affecting overall site performance.

Immediate steps to take:

1. Reboot your instances to see if that resolves the issue temporarily.

2. Check instance metrics in the Lightsail console to identify resource bottlenecks (CPU, memory, disk space).

3. Consider upgrading to larger Lightsail instances if you're consistently hitting resource limits.

4. Implement caching solutions for WordPress to reduce server load.

5. Optimize your WordPress installations by removing unnecessary plugins, optimizing databases, and compressing images.

The timing with the AWS outage and daylight savings change is likely coincidental, though it's possible that some recovery processes after the outage could be affecting performance if resources are still being rebalanced or if there were any configuration changes during recovery.

Sources
Website Capacity Issues on Amazon Lightsail | AWS re:Post
Webpage is loading slow | AWS re:Post
Website not loading | AWS re:Post
Wordpress website on Lightsail keeps dropping offline/unavailable | AWS re:Post