Yes, the reason is simple: your applications are using too much disk space on the EC2 instance (a Kubernetes node where it is running on).
Several possibilities and solutions:
You don’t expect to have data stored on your containers as they are supposed to be stateless (could be logs, dumps, temporary files…). I advise you to connect to your containers, find where this leak could come from, and fix the issue. You can use the Qovery Shell to help you on connecting to containers: CLI | Docs | Qovery
It’s expected, but those data are temporary, nothing important. You want more space to avoid running out of space on your Kubernetes nodes. So you can upgrade the current disk size on your cluster and redeploy. All your containers will benefit from a larger disk size.