Q.ACERS In Pots
I POTTED MY NEW ACERS INTO LARGE POTS TEN WKS AGO THINGS HAVE GONE FINE UNTIL LAST WK WHEN I NOTICED THE LEAVES TUNRNING BROWN THEY ARE YOUNG TREES AND ARE IN A SUNNY POSITION COULD THIS BE CAUSING THE PROBLEM OR IS IT SOMETHING MORE SINISTER ,
Certified GKH Gardening Expert
This looks more like an issue with overly wet soils. Soil will need a chance to dry out down to about 5-8 cm, thoroughly, between waterings.
I would apply a fungicide, and make sure to measure soil moisture if you are unsure of whether it is time to water or not.