cybersix,
I think most of what I see on your plants is the result of aging of the outer leaves. It also looks like some leaf streak to me. I end up with a lot of leaves like that and I just go around pulling brown dead leaves and yellow dying leaves to keep the plants looking good. Really, I don't know what the long term results of that will be because my daylilies have only been in my garden a few years.
I think the main thing about determining if you need to water more or not is to be determined by the soil. You, mention having clay soil, the important thing then becomes drainage! Does the water drain well, or does it stay puddled up around your plants. I think daylilies can stand lots and lots and lots of water, but they should not have their crowns under water and should have good drainage around the crowns, the longer roots seems to love lots of water.
You sound like the perfect candidate for mulch, put about two inches of mulch over the top of the soil to keep the soil and the roots cooler and earthworms feed. When you see the mulch wearing thin, replace it with more. You will build up your soil, feed the worms, and the daylilies will flourish.
