Password Hashing Security Using Scrypt & Argon2
This home-made construction is pointless and unnecessarily complex, Complexity is often the source of vulnerabilities. In this case, for example, I’ll wager you’re not securely handling the intermediate variables as you chain the multiple password hashes together.

Simply use argon2 only and increase the work factors. “Double scrypt” is fairly meaningless as scrypt also has work factor parameters which can simply be increased.