Water shortage. Evenly moist is the key to success.
its hard to over water strawberries expecially in a raised bed or pot, they like lots of water!
Did yo stick your finger in the soil to check?
Ill stick my finger in but I water them every 3-4 days and they are loaded with mulch! But ill check.
I thought I'd add I have sequoia and chandler berries planted in the same area. It's only affecting most of the chandler.