Issue retrieving certs for mutiple domain providers

I have multiple domain providers, in my case, DuckDNS and Cloudflare. I would like to retrieve certificates for both. In trying to do this, I passed in the following flags into my Traefik v2 container:

# DuckDNS
- --entrypoints.websecure.http.tls.certresolver=duckdns
- --entrypoints.websecure.http.tls.domains[0].main=${FQDN}
- --entrypoints.websecure.http.tls.domains[0].sans=*.${FQDN}
- --certificatesresolvers.duckdns.acme.email=${EMAIL}
- --certificatesresolvers.duckdns.acme.storage=/etc/traefik/acme/acme.json
- --certificatesresolvers.duckdns.acme.dnschallenge.provider=duckdns
- --certificatesresolvers.duckdns.acme.dnschallenge.resolvers=1.1.1.1:53,8.8.8.8:53
- --certificatesresolvers.duckdns.acme.dnschallenge.delayBeforeCheck=90

# Cloudflare
- --entrypoints.websecure2.http.tls.certresolver=cloudflare
- --entrypoints.websecure2.http.tls.domains[0].main=${FQDN2}
- --entrypoints.websecure2.http.tls.domains[0].sans=*.${FQDN2}
- --certificatesresolvers.cloudflare.acme.email=${EMAIL}
- --certificatesresolvers.cloudflare.acme.storage=/etc/traefik/acme/acme.json
- --certificatesresolvers.cloudflare.acme.dnschallenge=true
- --certificatesresolvers.cloudflare.acme.dnschallenge.provider=cloudflare
- --certificatesresolvers.cloudflare.acme.dnschallenge.resolvers=1.1.1.1:53,8.8.8.8:53
- --certificatesresolvers.cloudflare.acme.dnschallenge.delayBeforeCheck=90

Then for environment variables, I set:

- DUCKDNS_TOKEN=${DUCKDNS_TOKEN}
- CF_API_EMAIL=${CF_API_EMAIL}
- CF_API_KEY=${CF_API_KEY}

Now, when I run the container, the only certificate that is retrieved is for my DuckDNS domains. Whereas the entries for Cloudflare just have null values.

Example of acme.json:

{
  "cloudflare": {
    "Account": null,
    "Certificates": null
  },
  "duckdns": {
    "Account": {
      "Email": "---REDACTED---",
      "Registration": {
        "body": {
          "status": "valid",
          "contact": [
            "mailto:---REDACTED---"
          ]
        },
        "uri": "---REDACTED---"
      },
      "PrivateKey": "---REDACTED---",
      "KeyType": "4096"
    },
    "Certificates": [
      {
        "domain": {
          "main": "---REDACTED---.duckdns.org",
          "sans": [
            "*.---REDACTED---.duckdns.org"
          ]
        },
        "certificate": "---REDACTED---",
        "key": "---REDACTED---",
        "Store": "default"
      }
    ]
  }
}       

How can I retrieve certificates that are valid for multiple domain providers?