Instead of using a deployment with 3 replicas, use 3 deployments with 1 replicas each (or just create pods only); deployment1 -> pod1, deployment2 -> pod2, deployment3 -> pod3
Expose all the deployments on a separate service, service1 -> deployment1, service2 -> deployment2, service3 -> deployment3
Create an ingress resource and route to each pod using the service for each deployment. For example: