The black marks I mentioned are shown here. I admit I do water them every day with a healthy amount of water - I'm always concerned re the Texas heat that they don't have enough water - if the marks ARE overwatering vs. disease - can y'all suggest how often I should be watering them? :)

Long legged flies are, indeed, good guys. The black stems can be iffy to diagnose. Sometimes, it's normal discoloration while other times it can be an indication of problems.

If the discoloration is mostly at the nodes and leaf axils, it 'can ' be a sign of fusarium.

Water should be applied when the plant needs it. Water deeply (for a long time) on a less frequent basis in order to promote deeper, more vigorous roots. How often will be determined by temperature, humidity, rainfall, soil type, plant maturity and vigor, time of year, the presence of mulch, etc.

thank you!!

I think the dark coloration at the nodes is a normal condition for your plants.

That was my first thought, too, jean.

Long legged fly = Condylostylus mundus.
"The long legged fly eats soft-bodied invertebrates. Adult flies are predaceous on small mites , Aphids and flea hoppers, booklice, thrips, flies, silverfish, small caterpillars and other insects. You really want to have this little guy in your yard and in your garden. He is a very beneficial little guy."( from Wordpress.com)