The problem is that this mnemonic (passphrase) are not standard like 12 or 24 words seed + the words are not from the standard words list.
My mnemonic (passphrase) have different lengt, like 14, 17, 19 words
As you say, these are not BIP39 seed phrases but rather sound like the old style blockchain.info specific recovery phrases.
Have you tried inputting them to their old wallet recovery tool? Link here:
https://login.blockchain.com/wallet/recover-wallet