How is your drainage? This looks to me like classic overwatering and/or soggy soil. In any case they need to dry substantially between waterings.

Besides soil moisture, the soil should be able to be aerated, which is why raised beds and loose soils help. Also, was there a sudden change of temperature, especially from warm to hot?

Make note on Hot Lips of how much red is in the flowers. Fertilizing this one during summer heat should not only increase growth, but generate redder flowers. The larger the red zone in the flowers, the more active the plant is in growth. Older, larger plants will show whiter flowers than young, faster growing ones.

Are the plants next to more aggressive plants that may be encroaching on the Hot Lips root zone, or are keeping it from needed expansion?