Can create one figure but not another in matplotlib/pyplot

I am trying to use PyPlot to display multiple graphs in a single window. I can do that no problem with the following code:

def create_figure_one(self):
    plt.figure(1)
    plt.subplot(311)
    plt.plot_date(self.dates, self.PREC, '-', color='b')
    plt.title('Precipitation', fontsize=20)
    plt.ylabel('MM/DT', fontsize=15)
    plt.tick_params(axis='both', which='major', labelsize=10)
    plt.tick_params(axis='both', which='minor', labelsize=10)
    plt.grid()

    plt.subplot(312)
    plt.plot_date(self.dates, self.PET, '-', color='b')
    plt.plot_date(self.dates, self.AET, '-', color='r')
    plt.title('Evapotranspiration', fontsize=20)
    plt.ylabel('MM/DT', fontsize=15)
    plt.tick_params(axis='both', which='major', labelsize=10)
    plt.tick_params(axis='both', which='minor', labelsize=10)
    red_patch = mpatches.Patch(color='blue', label='Potential')
    blue_patch = mpatches.Patch(color='red', label='Actual')
    plt.legend(handles=[red_patch, blue_patch])
    plt.grid()

    plt.subplot(313)
    plt.plot_date(self.dates, self.Q, '-', color='b')
    plt.title('Flow', fontsize=20)
    plt.ylabel('CMS', fontsize=15)
    plt.xlabel('Time', fontsize=15)
    plt.tick_params(axis='both', which='major', labelsize=10)
    plt.tick_params(axis='both', which='minor', labelsize=10)
    plt.grid()

    plt.show()

This function gets called after clicking a button in my GUI. Similarly, I have another button in my GUI which calls another function:

def create_figure_two(self): 
    plt.figure(1)
    #UZTWC
    plt.subplot(611)
    plt.plot_date(self.dates, self.UZTWC, '-', color='b')
    self.title('UZTWC', fontsize=15)
    plt.ylabel('MM', fontsize=10)
    plt.tick_params(axis='both', which='major', labelsize=10)
    plt.tick_params(axis='both', which='minor', labelsize=10)
    plt.grid()

    #UZFWC 
    plt.subplot(612)
    plt.plot_date(self.dates, self.UZFWC, '-', color='b')
    self.title('UZFWC', fontsize=15)
    plt.ylabel('MM', fontsize=10)
    plt.tick_params(axis='both', which='major', labelsize=10)
    plt.tick_params(axis='both', which='minor', labelsize=10)
    plt.grid()

    #LZTWC 
    plt.subplot(613)
    plt.plot_date(self.dates, self.LZTWC, '-', color='b')
    self.title('LZTWC', fontsize=15)
    plt.ylabel('MM', fontsize=10)
    plt.tick_params(axis='both', which='major', labelsize=10)
    plt.tick_params(axis='both', which='minor', labelsize=10)
    plt.grid()

    #LZFPC 
    plt.subplot(614)
    plt.plot_date(self.dates, self.LZFPC, '-', color='b')
    self.title('LZFPC', fontsize=15)
    plt.ylabel('MM', fontsize=10)
    plt.tick_params(axis='both', which='major', labelsize=10)
    plt.tick_params(axis='both', which='minor', labelsize=10)
    plt.grid()

    #LZFSC 
    plt.subplot(615)
    plt.plot_date(self.dates, self.LZFSC, '-', color='b')
    self.title('LZFSC', fontsize=15)
    plt.ylabel('MM', fontsize=10)
    plt.tick_params(axis='both', which='major', labelsize=10)
    plt.tick_params(axis='both', which='minor', labelsize=10)
    plt.grid()

    #ADIMC 
    plt.subplot(616)
    plt.plot_date(self.dates, self.ADIMC, '-', color='b')
    self.title('ADIMC', fontsize=15)
    plt.ylabel('MM', fontsize=10)
    plt.tick_params(axis='both', which='major', labelsize=10)
    plt.tick_params(axis='both', which='minor', labelsize=10)
    plt.xlabel('Time', fontsize=10)
    plt.grid()
    plt.show()

But nothing happens. I don't get any errors in my terminal, my program doesn't terminate, and no window with my graphs appears. I can't see what differences between my two functions could possibly account for why the first is working and the second isn't.

self.dates:

    self.list_of_datetimes = []
    skipped_header = False;
    with open(data_file, 'rt') as f:
        reader = csv.reader(f, delimiter=',', quoting=csv.QUOTE_NONE)
        for row in reader:
            if skipped_header:
                date_string = "%s/%s/%s %s" % (row[0].strip(), row[1].strip(), row[2].strip(), row[3].strip())
                dt = datetime.strptime(date_string, "%Y/%m/%d %H")
                self.list_of_datetimes.append(dt)
            skipped_header = True

    self.dates = matplotlib.dates.date2num(self.list_of_datetimes)

If anyone has any insight it would be greatly appreciated.