For your next birds, look at some of the breeds that do well in hot climates, with big combs and smoother feathering. Here in the frozen north, I avoid them, but you have many choices in that category.
Mary
So sorry! That's horrible heat!!! You did what you could, but that was just too much for them.
Yes, you can integrate new birds with your two adults,, gradually, with plenty of space. Consider getting birds who can handle heat better, rather than those cute big fluffy ones. And Speckled...