Acer C720 Chromebook have delayed start up

Just as of last week many of our C720s have a delayed start up. Previously they would start up in 7 seconds. But now it's a good 20 seconds. When opening the device to turn on, it starts up in a black screen for nearly 20 seconds before it gets to the login screen. Many students/teachers have reported it to me. They think it is "broken", but for now, I told them them as long as they see the blue light when they turn it on they have to be extra patient to let it start up. I just wanted to bring it to your attention in case others are having the same issue. my samsungs/hp chromebooks are still fine on start up so not sure if it's a software issue. I did factory reset a couple but the same delayed start up happens.