Could be wind damage. Dry winds (which cold winds typically are) will dry out leaves, especially tender new ones on tips. We had cold in recent nights, but was above freezing (around 36F or so), and I lost a few tips, plus the edges of some of the leaves. I think it was because there were steady winds (seemed around 15-20mph), with gusts to around 30mph. The winds kept up for about 48 - 60 hours.
Mike central NY state, zone 5