You need to name your glyph with the name= attribute on the glyph that you are interested in having the hover tool active for and then set that name in the hover tool's names= attribute. (Note the name= attribute of the fig.line glyph in the example below.
hover = HoverTool( mode='vline', line_policy='nearest', names=['ytd_ave'],
    tooltips=[
        ("Week Number", "@WeekNumber"),
        ("OH for the Week", "@OverHead{0.00}%"),
        ("OH Average", "@AveOverHead{0.00}%"),
        ("Non-Controllable Hours", "@NonControllableHours{0.0}"),
        ("Controllable Hours", "@ControllableHours{0.0}"),
        ("Total Hours", "@TotalHours{0.0}"),
    ]
)
fig = Figure(title='Weekly Overhead', plot_width=950, plot_height=400,
         x_minor_ticks=2, tools=['pan', 'box_zoom', 'wheel_zoom', 'save',
                                 'reset', hover])
ch = fig.vbar('WeekNumber', top='ControllableHours', name='Over Head', 
         color='LightCoral', source=sources, width=.5)
nch = fig.vbar('WeekNumber', bottom='ControllableHours', top='TotalOHHours',
         name='Non-Controllable Over Head', color='LightGray', 
         source=sources, width=.5)
bh = fig.vbar('WeekNumber', bottom='TotalOHHours', top='TotalHours',
         name='Project Hours', color='LightGreen', source=sources,
         width=.5)
ave = fig.line('WeekNumber', 'AveOverHead', source=sources, color='red',
         y_range_name='Percent_OH', name='ytd_ave')