No, they are not normal... It's normal for an unregulated power supply that the voltages drops with load... But most switching power supplies are regulated... (your's sure is, because the load of the circuits of the TV is not constant) Either by sensing the current in the primary of the transformer, either the voltage in the secondary, or both in many cases... Try to check the voltage reference in the secondary side, see if it's within specs, and that it's stable (regarding of the load current)... If there is no sign of bad caps, most probably they are ok...
There are many possible causes like: the voltage reference, the optocoupler, the switching transistor... What IC does it use ?