Umm... I think that the push to add cal/mag is a little overzealous, in this case.
My plants look EXACTLY like that after heavy rains, and my climate is the most similar.
You are going to have to keep the plants dry, period. Problem: heavy rains interfere with normal uptake of nutrients, as you are essentially "flushing" the soil, repeatedly. This is the inverse of what happens in a calcium deficiency. (lack of calcium makes nutrients unavailable, by reducing uptake) But it looks exactly the same. The soil you've built is calcium sufficient. Your plants would never have gotten that green and that shape, if you had a calcium problem. And beds built with soil are nowhere near as problematic with calcium as container culture, with soilless mixes.
Please don't waste your money on Cal/mag. It's not your problem, right now. Definitely check the PH, and definitely try to get them dry, if you can.