Definitely get your soil analyzed. Dessert soils can have some strange problems. In L.V., I finally just dug a trench and back-filled with real soil.
My vote is too much water. Over watering does exhibit general yellowing of the plant. When I look at your leaves I do notice green veins though. Over watering does present quite a few odd behaviors in plants, however if it is not the problem then it IS a micronutrient problem. The above advice should do the trick, but first I would water every other or every third day, not every day. It is 100 where I live too and the plant can handle those temps.
Mine turned yellow exactly like yours did. Only on the new growth. And mine have completely stalled out! I suspected to much water since mushrooms are popping up around them......... lol.
I have not watered them myself yet though, but it has rained almost 3 times our normal amount this year. Not sure if to much water will cause them to stop growing or not though.
Good Luck to you, looks like they are still holding on, if you knew exactly why they are acting like that, I am sure you could bring them back!
I dunno, but it seems to me that in your environment I'd be wary of not giving your plants enough water. Looks like they already got cooked when you cut back. Perhaps you should monitor the moisture in the soil to figure out a watering schedule.
Wanted to add:
I'm not sure what kind of flow drip irrigation has, but 5-7 minutes doesn't seem like the watering would be very deep, which might be why it dried up so quickly.
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