Insufficient gpu problem!

There are 1 master and 4 nodes server in my k8s cluster, and I set up 4 gpus for each node server. The information such below:

NAME     GPUs
master   <none>
node1    1
node2    1
node3    1
node4    1

My problem is: Each of my jupyter users applies for 1 GPU, but when the fifth user creates a jupyter notebook, the error “0/5 nodes are available: 5 Insufficient nvidia.com/gpu” appears. Can not exist two users on a node? My jupyterhub config such below:

proxy:
  secretToken: "XXXX"
  service:
    type: NodePort
    nodePorts:
      http: 30080
      https: 30443
hub:
  extraConfig: |
    c.JupyterHub.spawner_class = 'kubespawner.KubeSpawner'
singleuser:
  image: 
    name: jupyter/minimal-notebook
    tag: 5197709e9f23
  profileList:
    - display_name: "Default: Minimal environment(Without GPU)"
      description: "Default"
      default: true
    - display_name: "Datascience environment(With GPU)"
      description: "Nvidia Quadro P5000"
      kubespawner_override:
        image: ihades/cuda-notebook:0.1
        extra_resource_limits:
          nvidia.com/gpu: "1"
  storage:
    dynamic:
      storageClass: nfs-client 
    capacity: 20Gi
    extraVolumes:
      - name: shm-volume
        emptyDir:
          medium: Memory
    extraVolumeMounts:
      - name: shm-volume
        mountPath: /dev/shm
  memory:
    limit: 32G
    guarantee: 2G
  cpu:
    limit: .5
    guarantee: .1
  extraEnv:
    EDITOR: "vim"
    GRANT_SUDO: "yes"
  uid: 0
  cmd: null