USB accessories disabled

Hi, in the middle of working on a project, all of a sudden, this iMac (21.5-inch, Late 2013) I'm currently using in my school's library just randomly said "USB accessories disabled." I had my iPhone plugged into the keyboard, my flash drive, my external HD, and my iPod Touch all connected in the back next to my keyboard. The only way I could get the mouse to respond was to completely disconnect all of the USB devices (without ejecting the two disks properly). Now that I got the mouse to respond again, I plugged in everything except my ipod touch to the 4 usb ports in the back of this computer. I've never seen this message before... I'm on 10.14.6. Would this issue be resolved with the supplemental update installed? The other iMac I normally use is completely up to date, so, I'm wondering if the missing update could be to blame... Thanks.