Answer: Wall 'O Waters absorb the sun's heat during the day and release it at night. With outdoor temps in the 90s, the temperature inside the Wall o' Waters could be in the hundreds, causing plants to wilt and burn (creating the brown spots). It's best to remove Wall o' Waters and other types of hot caps once summer temperatures arrive.
To help your plants recover, keep soil consistently moist and apply 2-3 inches of mulch around the plants to help maintain soil moisture and moderate soil temperatures. Since the stems and some foliage looks healthy, that's a good sign.
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