It's about the right time for spring sickness, is there any forsythia flowering in your area right now? We tend to use that as a marker. The freezes didn't cause it, spring sickness starts before the shoots emerge, it just takes a while for the damage to grow out to where you can see it. Sometimes this seems to coincide with a freeze, just because of the time of year it happens, but spring sickness happens with or without freezes. Freezing of the leaves can let in the leaf streak fungus and result in yellow and brown leaves but that's not the same thing. For it to be spring sickness there'd be bending, possibly stunting, and brown ragged "saw-tooth" leaf edges.
