Impatiens downy mildew would be my guess

Looks like ground frost damage. It was really cold down here this morning.

You asked this before, a week or so ago, without photos. The first photo looks typical of one that's experienced sudden frost, but if its been dying slowly since you first posted your question, coupled with the fact that these do look like Impatiens walleriana rather than New Guinea hybrids, this variety has a huge problem because they are very prone to attack from Downy Mildew, for which there is no treatment. That's why most garden centres don't sell them any more, even the growers can't keep the infection at bay... You're lucky to have got away with it up to now...