It could be a couple of things. Firstly, has it had water put on the leaves and then been in strong sunlight as this can act as a lens and scorch the leaves. Or maybe it has recently been put in a new situation (freshly bought? or moved position in the house/room) and it hasn't got accustomed to the atmosphere yet? Or it could be in a draught or too dry an atmosphere? Sorry, that's more than a couple!! Try mist-spraying regularly. New leaves should be OK.