When you have a wet dream and the semen gets on your clothes and u put that piece of cloth in the washing machine ... Do i the wash the whole load again or just that cloth?

This depends on how the clothes were washed and what type of machine was
used.

In principle, if after the clothes have been washed, there still remains
traces of semen in such a way that it could very easily be removed by
another wash then it must be washed since this proves that the first wash
was not effectice. This will apply to all the clothes in the load. Once you
are satisfied and convinced that the clothes are clean and pure, then this
is sufficient.

and Allah Ta'ala Knows Best

Mufti Ebrahim Desai