The best thing you can do is give them more water because planting a tree like that in June means copious watering - don't just use a wateringcan-full - leave the hosepipe on it for 5 minutes when you're watering it.
Don't feed it at this time of year either or the growth will be soft and when the weather gets colder again (end of Oct) you run a high risk of that new growth being frosted and killed, so feed it in the spring.

Another factor to consider after watering is it's position.
These will suffer badly from windburn if they're in an exposed position.

Thanks for your reply Louise1 yes I do think that might be the problem re watering as I did't water it that much when I planted it, so I hope it's not to late now.