Well, the first thing I would check is the watering. Potted and newly planted (< 1 year in ground) Acers need religious watering to avoid foliage damage. Every time they wilt, they come back browner.

The second thing I would check is the exact sun exposure. If they are in semi-shade, but the sun they get is in the hottest part of the day, they will get browning. 'Senkaki' might eventually adapt to the afternoon sun, say in a year or two, but the 'Purpureum' isn't likely to.

The third thing to check is the water quality. If the tap water you are using is very hard, or is run through a water softener, or is close enough to the coast to be brackish, the alkali and/or sodium is going to cause problems, including brown edges and chlorosis.

All of this is assuming that the new growth is being damaged, too, and it's not just left over damage from the drought this past summer.

The leaves of A. palmatum 'Senkaki' should be pale yellow green through summer, and yellower in autumn. The contrast with the red stems is lovely. If yours has green leaves, I might question its origins. I've got all mine in part shade as 'T' says, and out of drying winds which are more damaging than the sun. Phil J

Thanks guys. I'm pretty sure its not a watering prob, if anything the potted one could have been too wet and has some moss on the soil surface. It does look to me as if something has got at the Purpureum, it is much younger ( 2 yrs old max ) where the Senkaki is 4 yrs + I know some plants can take a year or so to aclimatise so will just keep an eye on things. Ps Philjeffs...the Sensaki does have pale green leaves and new growth is coming through paler still. No red stems tho. Too early, or has Wisley stiched me up? Surely not. Thanks again and all the best. Shimmyshyster.