Trailing Lobelia Going Mouldy
They are in hanging baskets and are watered reguarly and the baskets drain well.
Traditionally lobelia looks bad in heat and too wet environments. It could be either or both, and powdery mildew could be present. Don't know how to control heat, except to provide shade in hottest part of the day. If it's too wet, keep out of rain. and if powdery mildew is present, this article should help: https://www.gardeningknowhow.com/plant-problems/disease/get-the-cure-for-powdery-mildew.htm