This is a tricky one to diagnose via photo.  According to the literature, False Indigo (Baptisia australis) is tolerant of most soils so long as they are well-drained and has no serious pests and disease, although sometimes they have fungal issues like leaf spot, powdery mildew, and rust, and certainly Denver's cool, wet spring encouraged fungal diseases this year.

That said, your comments suggest to me it may not be fungal. Specifically, you write 1) you've had other plants in the same bed in previous years that showed the same symptoms, and 2)  you've had plants in containers in the same area that have shown similar symptoms.

Plant diseases are typically host-specific so the fact that other plant species in previous years showed the same symptoms suggests the underlying cause may not be related to this spring's weather but may be environmental or cultural. And assuming you used imported soil in your containers, we rule out soil as the underlying cause of the Baptisia's yellowing and necrotic tissue.

Yellowing is often a sign of too much or too little water. Here the black, necrotic tissue appears to first manifests on the leaf margins, then progress to the interior. There also are several dark lesions on the stems closest to the door which are curious, but may indicate over-watering and/or lack of oxygen at the roots.

If these are watered by drip emitters, check the emitters to see how much water is being delivered and that the emitters aren't set too close to the roots. You may have to dig around in the mulch to find all of them then note whether the emitters are 1/2 gallon per hour, 1 gallon per hour, or something else.  Also use a probe like a screwdriver to get a sense of whether the water is draining because, obviously, the homes in Central Park are new construction, the soils are shallow, and for the most part heavy clay. I can't explain why the north plants look green and healthy but the south ones look yellow and sickly.  Maybe they are on different zones or the line that connects them runs under the sidewalk and is damaged in some way. It may be that you are applying the proper amount of water but for some reason, it's just sitting at the roots in this bed like a bog.

Since I can't rule out fungus entirely, particularly septoria, it wouldn't hurt to implement the management recommendations for fungal issues:  avoid overhead irrigation, increase air circulation, and rake up & discard leaf debris in the fall to prevent pathogens from overwintering and re-infecting next year's foliage. From these photos, it looks like you've already got the first two covered.

Lastly, if investigating the irrigation situation doesn't resolve the problem, contact the Jefferson County Plant Diagnostic Clinic at the Jefferson County Fairgrounds where, for a small fee, trained clinicians can examine the plants:

https://jeffco.extension.colostate.edu/horticulture/clinic/