u/ChubbyChaser55

Does anyone know what this is from. Overwatering, over fertilizing or when I covered them for one cold night?

I know there is some fertilizer in the plant when I buy it. I mixed feeding topsoil with the native soil when I planted. Lastly I used a bit of miracle grow quick start when I planted it.

The rest of my plants are fine but I know hydrangeas are fragile.