The weather has been very unseasonable in Australia recently, particularly along the east coast. Summer didn’t really eventuate. We’ve had the occasional very hot day, but then later that day or the next day it’s been cold again.
When temperatures suddenly rise, new growth on plants doesn’t have time to harden off and the leaves get sunburnt. That’s what happened on the Wednesday before Australia Day – soaring temperatures and hot winds caused horrific damage in gardens. So many plants were burnt it looked as if a forest fire had blazed through and left a trail of devastation.
If your plants were sunburnt, give them some TLC. Fertilise, mulch and water them and eventually they will recover. Cut off the dead looking bits if you like, but wait another month or so in case they reshoot.