I have a Thalictrum rochebruneanum meadow rue. It is very tall, but the foliage is turning yellow. Would you know why? It gets sun in the early part of the day and then some more in mid afternoon.
Yellowing Foliage on Meadow Rue
Often when plant leaves turn yellow, and there are no bugs around, the plant needs more water. Why don't you try that first to see what happens. Here's an article on meadow rue: https://www.gardeningknowhow.com/ornamental/flowers/meadow-rue/growing-meadow-rue-flowers.htm