We know for an irreversible process, $\mathrm dS\gt\mathrm dq/T$.
And if the process is done at constant pressure we can take the equation as $\mathrm dH-T\,\mathrm dS\lt0$.
And we defined Gibbs energy, $G=H-TS$. At constant temperature and pressure $\mathrm dG\le0$.
But the fundamental equation of Gibbs energy $\mathrm dG$, in terms of temperature and pressure is given by $\mathrm dG=V\,\mathrm dp-S\,\mathrm dT$.
And as per our original conditions, i.e. at constant pressure and temperature for an irreversible process the value $\mathrm dG$ should be less than zero.
I cannot understand for the same condition the two equations give different answers.