I have a site that has been running out of memory on the server:

Log message:

[04-Aug-2026 16:01:05] WARNING: [pool mywebsite.com] server reached max_children setting (13), consider raising it[04-Aug-2026 16:01:05] WARNING: [pool mywebsite.com] server reached max_children setting (13), consider raising it 

Does anyone know how to go about diagnosing the cause of this?

A bit about the website:

• Wordpress block theme
• 1.3M visitors in past 12 months
• News website publishing avg. 450 posts per month
• Accessed and used all day by about 15 editors and marketing users
• Lots of plugins (20+ active) including:
  • Ad Inserter
  • Advanced Custom Fields
  • Conditional Blocks Pro
  • Default Featured Image
  • EWWW Image Optimizer
  • GDPR Cookie Compliance
  • Missed Scheduled Posts Publisher
  • OneSignal Push Notifications
  • Perfmatters
  • Rank Math SEO
  • Site Kit by Google
  • Social Sharing Block
  • Wordfence
  • WP Mail SMTP
  • WP Popular Posts
  • WPCodeBox 2
  • WPForms
  • WPForms Campaign Monitor

This is the only site I have which has so much going on and is also so heavily used and visited.

I'm interested to learn how to start diagnosing performance issues generally and any insight anyone can give as to how to do that would be much appreciated.