A: What you describe is a common problem for those of us diligently watering our containers to get them through an oppressive Summer. Your potted flowers do need steady moisture to get through the heat, and you’re probably watering them appropriately, but this kind of heavy watering in containers has its own set of problems.
Your likely issue is the need to fertilize your flowers. Even if you’ve regularly fed them previously, or planted the flowers up with time-release fertilizer, the heavy irrigation you’ve been giving will cause your fertilizer to expend faster, to leach out of the container’s soil, leaving your flowers without the nutrients they need to grow properly.
If you’re using water-soluble fertilizer, feed weekly at normal rates, or constant-feed at low rates with each watering. If you’re using time-release granules, work them into the top of the soil to reduce washing out granules over the lip of the container, and presume the duration of whichever granular slow release product you’re using will be shortened by somewhere from a third to half of its normal time. (Example: a 3-4 month formulation will last 2 months at best.)
As long as you’re watering this much, simply keep an eye on your flowers in containers, and fertilize them frequently if they show signs of weak growth or show pale leaf color. Mulching your containers properly and adding Soil Moist to your container soil when planting flowers will help, too.
Please note: Begonias, impatiens, and petunias from spring would look battered if they’re still alive at all after the heat we have been experiencing. Don’t waste time on those at this point; clean out your containers, and plant new color that’s appropriate to the heat.