Mostly the hard fork wallets use seed or recovery phrase to claim those altcoins, tho what are those hard forks you're trying to claim? Anyway, blockchain.info are completely out of this issue, its either there are some malware/keylogger/phishing wallets are injected on those wallets/software you used claiming the hard fork coins.
The addresses used across those forks are the same. Seeds/recovery phrase are used to derive the private key and then to import the addresses. Blockchain.info does use seeds though some addresses generated in the past are independent of it.