Console Spam: Mob spawning with custom items

Hi there MM community. So, I have had this problem for awhile now and I am just wondering if there is a way to reduce this spam in my server console. (Paste Bin at bottom) I'd like for these messages to completely be gone as I can not monitor my server as efficiently now. I've looked through all my files and no luck. So if you have heard of this problem and/or know how to fix, help would be greatly appreciated. ~Kezzy

(Paste bin: https://pastebin.com/TJnVJcyH )