Apache ZOMBIES killing my apache, please help...

I don`t know what this can be but I know that this killing my apache every few minutes on 2 my servers and I think this is some attack or...

Server working fine, like before this problem but now I have too much zombies (when I use 'top' command) and from 0 in second come to 30 and back to 0 and back to 2x-30 and I think that that killing my apache...now I have too much:
httpd <defunct>

processes in apache...

Somebody know what can be problem?

Thanks.

 

 

 

 

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