FX working only for the channels of the music but not for the microphone

Hello again!

I have a question, i have the DDJ SX and when i want to use the effects ( reverb, echo etc,) I can apply them normally in the 1, 2 channels of the music when I enable the FX, but not when the channel is turned to the microphone!! why does this happen? can i fix that or i need to buy another device for having effects while singing... :/

Thank you