I seriously doubt that. A creature of literal gargantuan size wouldn't evolve without huge amounts of abundant food. Starvation does have impacts on bones as well, so it would be something the PDA could detect.
It's much more likely the Gargantuan leviathan died from something perfectly normal, and just happened to fall into the Subnautica crater.
Unless you're saying that because food ran low, the gargantuans fought each other and this one lost?