Legend only shows in one subplot matplotlib code example

Example 1: matplotlib one legend for all subplots

handles, labels = ax.get_legend_handles_labels()
fig.legend(handles, labels, loc='upper center')

Example 2: subplot matplotlib legend

ax1.legend("HHZ 1",loc="upper right")
ax2.legend("HHN",loc="upper right")
ax3.legend("HHE",loc="upper right")