Kafka connect plugins/connectors don't get installed properly using docker compose

This is how my docker-compose yaml looks like:

---
version: '2'
services:
  zookeeper:
    image: confluentinc/cp-zookeeper:6.1.0
    container_name: zookeeper
    environment:
      ZOOKEEPER_CLIENT_PORT: 2181
      ZOOKEEPER_TICK_TIME: 2000

  broker:
    image: confluentinc/cp-kafka:6.1.0
    container_name: broker
    depends_on:
      - zookeeper
    ports:
      - 9092:9092
    environment:
      KAFKA_BROKER_ID: 1
      KAFKA_ZOOKEEPER_CONNECT: zookeeper:2181
      KAFKA_LISTENER_SECURITY_PROTOCOL_MAP: PLAINTEXT:PLAINTEXT,PLAINTEXT_HOST:PLAINTEXT
      KAFKA_INTER_BROKER_LISTENER_NAME: PLAINTEXT
      KAFKA_ADVERTISED_LISTENERS: PLAINTEXT://broker:29092,PLAINTEXT_HOST://localhost:9092
      KAFKA_AUTO_CREATE_TOPICS_ENABLE: "true"
      KAFKA_OFFSETS_TOPIC_REPLICATION_FACTOR: 1
      KAFKA_TRANSACTION_STATE_LOG_MIN_ISR: 1
      KAFKA_TRANSACTION_STATE_LOG_REPLICATION_FACTOR: 1
      KAFKA_GROUP_INITIAL_REBALANCE_DELAY_MS: 100

  schema-registry:
    image: confluentinc/cp-schema-registry:6.1.0
    container_name: schema-registry
    ports: 
      - 8081:8081
    depends_on:
      - zookeeper
      - broker
    environment:
      SCHEMA_REGISTRY_HOST_NAME: schema-registry
      SCHEMA_REGISTRY_KAFKASTORE_BOOTSTRAP_SERVERS: broker:29092

  kafka-connect:
    image: confluentinc/cp-kafka-connect-base:6.1.0
    container_name: kafka-connect
    depends_on:
      - zookeeper
      - broker
      - schema-registry
    ports:
      - 8083:8083
    environment:
      CONNECT_BOOTSTRAP_SERVERS: "broker:29092"
      CONNECT_REST_PORT: 8083
      CONNECT_GROUP_ID: compose-connect-group
      CONNECT_CONFIG_STORAGE_TOPIC: docker-connect-configs
      CONNECT_OFFSET_STORAGE_TOPIC: docker-connect-offsets
      CONNECT_STATUS_STORAGE_TOPIC: docker-connect-status
      CONNECT_KEY_CONVERTER: org.apache.kafka.connect.storage.StringConverter
      CONNECT_VALUE_CONVERTER: io.confluent.connect.avro.AvroConverter
      CONNECT_VALUE_CONVERTER_SCHEMA_REGISTRY_URL: 'http://schema-registry:8081'
      CONNECT_INTERNAL_KEY_CONVERTER: "org.apache.kafka.connect.json.JsonConverter"
      CONNECT_INTERNAL_VALUE_CONVERTER: "org.apache.kafka.connect.json.JsonConverter"
      CONNECT_REST_ADVERTISED_HOST_NAME: "kafka-connect"
      CONNECT_LOG4J_ROOT_LOGLEVEL: "INFO"
      CONNECT_LOG4J_APPENDER_STDOUT_LAYOUT_CONVERSIONPATTERN: "[%d] %p %X{connector.context}%m (%c:%L)%n"
      CONNECT_LOG4J_LOGGERS: "org.apache.kafka.connect.runtime.rest=WARN,org.reflections=ERROR"
      CONNECT_CONFIG_STORAGE_REPLICATION_FACTOR: "1"
      CONNECT_OFFSET_STORAGE_REPLICATION_FACTOR: "1"
      CONNECT_STATUS_STORAGE_REPLICATION_FACTOR: "1"
      CONNECT_PLUGIN_PATH: '/usr/share/java,/usr/share/confluent-hub-components/'
    command: 
      - bash 
      - -c 
      - |
        echo "Installing connector plugins"
        confluent-hub install --no-prompt confluentinc/kafka-connect-jdbc:10.0.2
        confluent-hub install --no-prompt jcustenborder/kafka-connect-spooldir:2.0.60
        confluent-hub install --no-prompt streamthoughts/kafka-connect-file-pulse:1.5.0
        #
        # -----------
        # Launch the Kafka Connect worker
        /etc/confluent/docker/run &
        #
        # Don't exit
        sleep infinity
    volumes:
      - ${PWD}/data:/data

When I run docker-compose up -d it is all good but right after the containers are up, the one which holds schema registry exits. Then I start it once again and it works totally fine. The real problem is that when I execute the following command, I can not see any of my plugins installed:

curl -s localhost:8083/connector-plugins|jq '.[].class'|egrep 'SpoolDir'

I am following this tutorial more or less. I just skip the postgres container and also kafkacat and ksql.

EDIT This is what to logs say for the kafka-connect container:

Installing connector plugins
Running in a "--no-prompt" mode
Implicit acceptance of the license below:
https:/github.com/jcustenborder/kafka-connect-spooldir/LICENSE
Implicit confirmation of the question: You are about to install 'kafka-connect-spooldir' from Jeremy Custenborder, as published on Confluent Hub.
Downloading component Kafka Connect Spooldir 2.0.60, provided by Jeremy Custenborder from Confluent Hub and installing into /usr/share/confluent-hub-components
Adding installation directory to plugin path in the following files:
/etc/kafka/connect-distributed.properties
/etc/kafka/connect-standalone.properties
/etc/schema-registry/connect-avro-distributed.properties
/etc/schema-registry/connect-avro-standalone.properties

Completed

Running in a "--no-prompt" mode
Implicit acceptance of the license below:
The Apache Software License, Version 2.0
http://www.apache.org/licenses/LICENSE-2.0.txt
Implicit confirmation of the question: You are about to install 'kafka-connect-file-pulse' from StreamThoughts, as published on Confluent Hub.
Downloading component Kafka Connect File Pulse 1.5.0, provided by StreamThoughts from Confluent Hub and installing into /usr/share/confluent-hub-components
Adding installation directory to plugin path in the following files:
/etc/kafka/connect-distributed.properties
Adding installation directory to plugin path in the following files:
/etc/kafka/connect-distributed.properties
/etc/kafka/connect-standalone.properties
/etc/schema-registry/connect-avro-distributed.properties
/etc/schema-registry/connect-avro-standalone.properties

Completed

uid=1000(appuser) gid=1000(appuser) groups=1000(appuser)
===> Configuring ...