This is according to my text :

Well I understand why more of Elimination reactions happen at high temperature(I guess this is due to $\triangle\\\\$G being more negative due to multiple product formation as well) , but why do Substitution reactions have their yields decreased as temperature goes up?

This is according to master of organic chemistry; (Even though it says that there is a relative increase, the graph shows a $decrease$ in yield of the substituted products) :

Aren't they supposed to have their output increased as well,as the activation energy barrier has already passed and rate increases with increase in temperature, Or am I missing something fundamental here?

Also, what could happen just after the energy barrier is broken for any one of the reactions?