Could be too much sun or fertilizer burn.

Thanks. May be so.
I added Osmocote in Sept. Re potted it into a bigger pot last week.
What is the remedy?
Will try shifting to a shadier place and see.

Looks like scorched leaves to me too. Hydrangeas don't like intense sun. We grow them in dappled shade. What's your maximum temperature, Daisy?

Thanks Beattie.

Its been swinging between 70 F - 80 F in recent weeks here in San Jose, CA.

With regards to Osmocote; I don't know if this it your situation but my greatest gardening blunders (and other areas of endeavor too) is when I failed to " Read the label and follow the directions!). That useful and very simple piece of advice was from the late and great gardener Ralph Snodsmith(USA). Ralph was well known for giving gardeners very Down To Earth advice.

Let me see if it comes back in a shadier space.