I couldn't offer advice on whether or not to fire without criteria more specific than 'performance'. Presumably, you aren't hiring people to perform you're hiring them to get a job done-- and what specifically about that job has not been done that you need done?

Unclear expectations and confusing priorities can make motivation very difficult. You use the term 'performance' 5 times and I still haven't the slightest idea what these guys are supposed to be producing except that they are "technical." I understand you don't want to be identified and that's fine, but if you use this kind of imprecise language with your employees, they'll just nod and vaguely agree to get through the conversation. Five minutes later they'll realize the conversation was completely pointless.