Growing wild geranium in Omaha, NE
I planted two earlier this spring. One doing okay, flowered a little, other turning yellow... I did not water too much. It has rained more than normal here. It is strange that one plant doing okay and one doing bad... help! Kelly
Certified GKH Gardening Expert
It is likely that the rain has caused it to be overwatered, leading to root rot.
You will have to use a fungicide. This article will help: https://www.gardeningknowhow.com/garden-how-to/info/using-fungicides-in-garden.htm
Since there is quite a lot of genetic variability in plants, it is not uncommon for one to be immune, or a little better suited to handle certain diseases than another. This would explain why one is having issues and one is not.
This article will help you to grow geraniums: https://www.gardeningknowhow.com/ornamental/flowers/geranium/geranium-care.htm