What’s troubling a trio of plants?

I’m afraid that by the time they reached me your samples had rotted into a smelly, unrecognisable mush. However, I thought I could detect leaf spotting on the liriope and assume that the day lilies and irises had similar markings.
Although appearances may have been similar, it is unlikely that all three plants had the same disease. The problem with the iris could have been a condition known as iris scorch which is a physiological disorder caused by a water imbalance or inadequate drainage.
Now is a good time to lift and divide bearded irises anyway and it will enable you to keep the youngest, most vigorous rhizome sections and discard the rest. Plant new divisions in very free-draining soil and hope for a recovery.
All three plants can suffer from various forms of fungal leaf spot but although the symptoms are unsightly, the diseases are seldom fatal.
You could try spraying with a fungicide, but there is no guarantee that it will clean the plants up. It is better to make sure all the plants are growing in ideal conditions and hope that they will make a recovery as summer progresses.