Problems with a no. of begonias in large pots kept on a porch all summer

Question

even though they are deadheaded at least once a week, and kept watered, they are starting to show some sgns of dieback, or drooping leaves.

Answer 1

Perhaps they're getting too much water or aren't draining well enough. Begonias have thick stems and don't need a lot of water. The drooping may be due to stem rot from improper drainage. Check the situation with the soil in the pots and lightly feed them if you haven't already. A slow release balanced fertilizer will feed them all summer.

Here's a helpful article:

https://www.gardeningknowhow.com/ornamental/flowers/begonia/annual-begonia-care.htm