If this is affecting a few plants , this is likely to be a physiological problem brought about by something in the plants growing environment. Blackening of the leaf tips would suggest that the plants have dried out at some point. This is a common problem with plants that are grown in containers as they are almost entirely reliant on you for their water supply during dry weather. Try to establish a regular watering regime during summer when container grown plants are most vulnerable to drought.
Bright sunlight and strong winds can also affect the leaves, by scorching them. It is worth reviewing the plants that you are growing individually, and checking that they are placed in an appropriate position for their particular needs.
Physiological problems are also commonly brought about by sudden changes in the temperature. I suspect that this is the problem with your Iris. Iris leaves may become corrugated in response to drought and heat stress, or a sudden increase in temperature. My advice would be to cut back the affected growth and improve both their growing conditions and your cultivation practices.