My grapefruit tree is 11/2 years weak it's position fruit but the leaves are yellowing and it looks sick? I live in AZ, I fed the tree near Citrus feed and...

I live in AZ, I fed the tree near Citrus feed and I sprayed it with a instinctive home made bug repellent (main ingredient is garlic) and it began to look better but now it is looking sick again. Please Help, I don't want my tree to die on me!
How to bring rid of gnats who took...
Answers:    Its possible it could be getting over watered. i know when i dampen my plant to much there leaves get sickly. It could be also it is getting stressed out.