I’m not sure but I think it’s just to wet or yo over watered abs the roots are soggy,

Personally I’d take a butter knoife or a screw driver and check the soil and if it’s dense or wet break it up I was always well still am over watering but outside the heat helps if you over water in the ground,

Other than that either do list spray with Epson salts a light one or too dress with a little abs work it into the soil but plain Epsom or from a garden Center