Question Author
Found this article on-line, sounds like what my plants and possibly yours, are experiencing.
"It causes the petals and leaves of the plant to fall off, reducing them to bare stems.
Known as Impatiens downy mildew, it first appears as a white felt-like powder on the underside of leaves and spreads on airborne spores.
Gardeners have been urged to keep an eye out for the disease and to destroy any of the bedding plants displaying symptoms to stop the spread.
Scores have already contacted the Royal Horticultural Society about their dying busy lizzies.
Although commercial growers have been developing measures to control the disease, slow sales at the start of the bedding plant season meant that plants became crowded. This provided favourable conditions for the virus to spread and meant that infected plants may have been sold to the public.
Guy Barter, head of horticultural advisory services at the RHS, said that it was unclear where the disease was coming from.
He said:"There is always a danger that treatment with professional fungicides in the nursery can suppress but not eliminate the disease so that it breaks out later in gardens."
He said that there was no real remedy for the problem other than digging up infected plants and avoiding replanting busy lizzies in the same ground "
An explanation perhaps but not much help for my flower beds. I shall take the advice and dig them up, if only to perhaps gives the healthier ones a chance.