Step 3: Plant Scale
Yellowing leaves are only at the growing points of the affected plants. Older leaves are a healthy green and fully expanded. Compared to healthy plants, the yellow leaves seem smaller than the healthier new leaves of other flats. Growth rate appears to be slower, as the healthier plants of the same species are generally taller and fuller.
Roots appear to be healthy. They have filled the container and are mostly white, showing only a slight tan color.
Nemesia showing yellow tips with green leaves below.
Only the growing tips are affected in the purple annual phlox.