Sounds like there was a phoned-in tip, to which somebody responded and found blood on the porch and a foul smell coming from inside.
That sounds good enough to go back and get a warrant, to me. That the tip came from a “psychic” doesn’t really make much difference it seems, based on those facts.
I don’t see the police doing any wrong here. If they didn’t check this place out and there had been a mass grave, everyone would have been yelling they were lazy. So, there is a tip of a grave, containing children and they find blood. They also smell something rotting. Sounds like a warrant to find out if there were bodies is reasonable.