Hang fire on buying more seeds just yet - give the others time. I ended up throwing out some of my poly seedlings because most of the seeds I planted eventually germinated and I had too many!
I'm over wintering 2 one yr old seedlings indoors because I didn't know how they'd do outside for the first (UK) winter but the others outside are looking fine, despite out terrible, wet, storm weather for the last 3-4 weeks. Well, all bar the one that got smashed by hail. But I'm hoping that even that will rally once spring comes