Unfortunately we can't quite see enough detail in the photos to make a diagnosis. Are you able to resend larger photo files? (Ideally at least 1MB each, which will allow us to zoom-in.) If not, can you take closer photos of the mum and lavender symptoms? If you need to send more than three pictures, you can reply more than once, attaching different files each time, to get around the system limit of 3 attachments.

More information about their growing conditions may also help. Are they being monitored for watering needs now that regular rains have ended? Have they been growing in that location for a few years, or are they new additions? Direct sun from 9am to 1pm isn't quite enough to satisfy the needs of either of those plants, as they prefer full sun (6-8 or more hours of direct light in summer), but if they've flowered for you there in past years (and we see the lavender is blooming now), than it might suffice, though it will impact the plant's vigor and might make them more vulnerable to disease. (Sun helps to dry off foliage after dew or rain, and the longer the leaf surfaces remain damp, the more easily they can be infected by pathogen spores. A sunny location will keep the leaves drier than a semi-shade location.)

Miri

The Chrysanthemum leaves all across the yard have had the same blight as in the photo. The lavender usually survives well on the berm that is slanted toward the sun with 5 hours of sunlight. There are mature Oak and Cherry trees that shade over the lavender after 2 pm. Most of the blooms on the lavender have immediately gone dark grey. Is this a blight that will appear next year too?

Thank you for the additional photos and information. Could we trouble you for a closer, clearer picture of the lavender symptoms, please? We can't quite make out enough detail, such as whether the white markings appear to be on top of the leaf or pockmarks of tissue missing from the leaf. Placing a cutting or two on top of a plain piece of paper might help. We will consult with our plant pathologist to see if he recognizes the mum foliage damage, but a clearer photo of the upper surfaces of a few leaves (including some that are more fully brown) might help. Some of the old injury looks like Four-lined Plant Bug damage (made weeks ago, as the insects are not active now), but we can't be certain.

Miri

Our plant pathologist agrees that at least some of the damage (on both mum and lavender) may be due to prior Four-lined Plant Bug feeding. (Even though the insects are long gone, their feeding damage will remain for the life of that leaf. The linked page shows some damage on lavender, which tends to look different from this insect's damage on other plants.)

There could also be overlapping leaf spot infection on the mum (we can't tell which type, though Septoria can be common), plus some drought stress. He suggests cutting back the mum lightly to remove some of the damage (it would be like last-minute pinching, since mid-July is the cutoff point for ending pinching), plus trimming the lavender as well. (Please share close-up photos of the lavender symptoms before discarding the trimmings, though, if you don't think they match Four-lined Plant Bug damage.)

Miri

I think you have diagnosed the lavender correctly. The sample on the web page looks like what has infected the lavender.  I haven't seen an actual 4-lined Plant Bug but will be on the lookout. This drought is bad too.

Thank you

Thank you for the new photos, they are helpful and confirm that this looks like Four-lined Plant Bug damage. If useful, you can browse more photos of these insects on the linked page, which is a Maryland Biodiversity Project page for that species showing both adults and juveniles, since they are colored differently. Activity of this single-generation insect in Maryland peaks between mid-May and mid-June, and they are essentially absent outside of those times (especially by this late in the summer). Therefore, next year, you'd only need to start looking for them around early May.

Since they overwinter as eggs that female bugs insert inside plant stems, that makes preventing them more difficult (compared to eggs laid in dead leaf debris would could be removed), since it would take lots of pruning to remove most of the eggs, which on a shrubby perennial like lavender would compromise its health as well as its appearance.

Miri

Excellent help. Many thanks.

You're welcome.