Ask-a-Dave's-Gardener: Help! Sudden onset of yellow, curing leaves with brown spots, 5 by lizziec615

lizziec615 wrote:
Help! Came home from work today to find that most of the plants in my garden have diffuse yellowing of leaves with brown spots and curling edges. None of this was present and they all looked healthy to me on Tuesday evening. Any suggestions of what this is and how to treat it? I\'ve been struggling with a couple of the plants having some occasional leaf yellowing, but never any spots or curling until today and definitely never so diffuse. And even that yellowing had seemed to improve over the last week or so after we started weekly treatments with neem oil, fertilized once, and increased watering to 3x per week for 30 minutes with soaker hose. Would greatly appreciate any input or advice!! Thank you!