I don't know much about gardening. Just started a little rooftop garden during quarantine. I noticed some of my tomato plants were browning from the soil. It looks like the brown parts are not getting thicker but the rest of the plant does. Today while I was checking my plants one of the tomato plant just snapped like a dry branch. It had a lot of flowers and it got me worrying about my other plants.
This started a couple weeks ago, I saw a small insect/mite on one of the plant immediately took the photo and showed it to the place where I got the plants. He gave me a spraying solution and said it would both kill the mites and heal the brown plants. I dont see mites anymore but the browning issue is getting worse.
I water them daily and live in a sunny place and my plants get direct sunlight until 2-3pm.