High I/O & Memory usage usually indicates your site is getting hammered by traffic (most likely bots if your site doesn't already have quite a bit of traffic), your email function on the server may be compromised, or you have malware on your site. That's the 3 most likely causes of a sudden change like you describe, but it could also be something on the server itself.
GoDaddy doesn't do support through a ticket based or email system. You'll have to call phone support or hit up live chat if you want to speak with them about your issue. We'd also be happy to take a look on here if you provide the URL so we can take a quick peek.
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