Cisco switching issues

We have a stack of 3 cisco 2900 xl switches, all connected to a cisco fibre backbone switch. I’ve recently noticed when connecting printers etc that ports on two switches don’t light up as a device is connected, whereas one lights up instantly. I’ve checked (via visual switch manager (a java based web client thing) that all ports are set to autonegotiate speeds etc and that port fast is on, but this doesn’t help… any ideas???

Also , some devices are experiencing severely slow network access (i.e. copying off a 150 mb file takes 45 minutes as opposed to the usual 45 seconds).. could be related to the other problem???