That looks like a fungal disease on the one that is 'sick'. Not sure what though.

I did wonder if it is anthracnose which is fungal. Did the leaves have black spots/marks on the leaves?

I havent noticed any black spots...if it is fungal disease is there anything can do to aid recovery? Thanks

I planted a new Acer in a pot and that's gone the same way. I sent a photo to the garden centre and they said it was frost damage and that i should not remove those stems but use a Maxicrop liquid feed straight into the pot and not onto the plant. So far, with all the rain I haven't done it but the plant is now looking very sick. Hopefully, when fed, as the centre suggested, it will improve especially now the weather is forecast to warm up.