LTM pool showing as Red(down) and unable to connect before deadline

I have a couple pool members that are not responding to 443 monitors all of the sudden, It has worked fine forever but not it is in a down state while the port 80 monitors continue to stay green. is this most likely a health monitor issue? I wouldn't think so since it operated properly beforehand. the troubling part to me is that is down on 2 separate nodes both for 443. The only thing I can think is that it could be on the customers side but I am really not sure why it would be 443 only. any insight would be very helpful