To put it into perspective, without you giving an idea of what integration it is, and based on your average startup time. If they were to go 1 by 1 with each integration for 1.5 days (to see if it’s a memory leak) it would take approximately 8 years to find the integration as a worse case scenario.
So, go 1 by 1 with your integrations, remove each one and run it for a few days but start with the integrations that would probably have the issue. But remember, only do this if you can 100% say that core is what has the memory leak. Keep in mind… If your core memory stays the same throughout it’s 1.5 day life but it’s running out of memory, then it’s not core that’s the problem. Something else is eating up the memory and core get’s impacted by it.