How to start multiple poolboy workers

I am trying to start multiple poolboy workers in my application like this:

 def start(_type, _args) do
    children = [
      # Start the Ecto repository
      MyApp.Repo,
      # Start the Telemetry supervisor
      MyAppWeb.Telemetry,
      # Start the PubSub system
      {Phoenix.PubSub, name: MyApp.PubSub},
      # Start the Endpoint (http/https)
      MyAppWeb.Endpoint,
      # Start a worker by calling: MyApp.Worker.start_link(arg)
      # {MyApp.Worker, arg}
      :poolboy.child_spec(:generator, generator_poolboy_config()),
      :poolboy.child_spec(:summarizer, summarizer_poolboy_config()),
      :poolboy.child_spec(:analyzer, analyzer_poolboy_config())
    ]

But I get this error:

** (Mix) Could not start application my_app: MyApp.Application.start(:normal, []) returned an error: shutdown: failed to start child: :summarizer
    ** (EXIT) already started: #PID<0.600.0>

But if I comment out the other poolboy workers and leave only one everything runs. My question is how can I start multiple poolboy workers? Since it is an Erlang library I could not find any docs. Thank you!!