The simple answer is nothing is wrong with them! In fact, external condensation can be proof that energy efficient windows are performing well (see below).
The longer answer is that the modern windows that FENSA Approved Installers fit these days are so much more thermally efficient than those installed in decades past. As a result, the heat used to warm homes doesn't escape through to the outer pane.
The outer pane of glass is therefore cooler and when its temperature falls below dew point, moisture in the air condenses on it.
The reason window condensation can be worse during Autumn (and Spring) mornings is that at these times of year the temperature of the glass can really drop overnight, yet the dew point remains relatively high.
Some windows can be affected more than others and slight changes in orientation or shelter can mean that windows or even panes next to each other can react differently.
Unfortunately there is not much that can be done to stop this phenomenon. It usually doesn't last long and shows that the heat being used to warm your home is being saved rather than lost through your windows - thus potentially lowering your heating bills and reducing your home's carbon emissions.