NextJS strange high memory usage

I have a project with 2 nextjs apps: portal and webapp the portal is 99% static content. webapp has some interactions. both have very low traffic. the day before yesterday something happened and memory usage significantly increased. when I notice that I just restarted both and it became normal. What could be a reason of that? I suspect that for some reason it started revalidate/recreate pages. I see a message in logs: For production Image Optimization with Next.js, the optional 'sharp' package is strongly recommended. Run 'npm i sharp', and Next.js will use it automatically for Image Optimization. but I have sharp installed and before the accident memory usage was low project id: a827064e-dc8f-44cb-8e9c-41367a6e6fc1