warped or cracked are both possibilities. My guess would be that SOA are unlikely to give in on 'fair wear and tear' I know that when I cracked mine on my '94 WRX back home - there was nothing but my caning the brakes that caused it.
They get very very hot and then cool too quick and hey presto! a crack opens up along the vent vane line!
If they are cracked they need replacing - get slotted rotors to replace them. If they are warped - hope there is enough meat on them and get them machined and start saving for the slotted rotors!
PS: how high is 'high speed'??