Hi Basak, Congratulations on venturing into the world of tomato gardening.  Just for fun, maybe read the book The $64 Tomato to enjoy a great journey for a fellow newbie!

First, I have grown tomatoes in sunny, windy, dry north central Oregon for years.  I think your plants look vigorous and healthy, so don't beat yourself up.  Usually yellow leaves mean the plant needs fertilized and/or iron...if you didn't already add some gentle organic fertilizer to the planting hole, definitely get a tomato/vegetable fertilizer (liquid, granular or spikes) and follow label directions.  I myself have forgotten to fertilize my tomatoes during the growing season and have poorer harvests as a result.  Note, for your tomatoes in containers and/or shallow raised beds, with frequent watering comes washing out of nutrients, so you will definitely need to fertilize at least once a month during the summer.  Stop fertilizing by September to allow plants to stop growing and focus on ripening fruit. 

My tomato plants also have some of those dried up, curly leaves; I noticed it tends to be the oldest leaves at the bottom of the plant, so I'm wondering if there was some early growth stress?  I went out to my plants yesterday and just snipped off all those leaves and pruned back gangly stems.  When my plants start outgrowing my tomato cages/trellis, I "give'em haircuts" and keep pruning back the overgrown stems.  

Make sure to water long and deeply....preferably with a drip system or a soaker hose...so that the water can penetrate down at least 12-18 inches into the soil.  Only water at the base of the plant, not wetting the foliage, to avoid fungal problems.   If you use a hose, you will need to go around and water each plant deeply 2-3 times during one session in order to thoroughly wet the soil.  If you wonder how deep the water is going, dig down and see how moist the soil is at different levels.  I know I have been surprised how shallow hose watering usually is.  The "Seed to Supper" course from OSU suggests that if you are hand watering (like with a hose or watering can), water until the soil glistens, wait for it to soak in then water again, wait for it to soak in a second time and water again.  You are trying to grow a deep, strong root system, and roots "chase the water" down into the soil if you water deeply.  Optimally, your plants would only need to be watered once or twice a week, once the roots are established.  However since yours are in large containers (which dry out quickly and usually drain quickly) you will probably need to water every 2-3 days, especially in hot water.  Toward the end of the season, you will need to stop watering as an attempt to force the plants to finish ripening the fruit on them, by subjecting them to end-of-season stress.  

Flowers will often fall off without making fruit when going through a hot spell, like we've had recently.  The plant will usually continue to put out more flowers during the growing season.  If you are concerned, there are some "blossom set" type spray products at garden centers that you can spray on each flower to encourage fruit development.  

I think your spray is a nice, all-purpose one as it is labeled as a fungicide, insecticide, and miticide as it is neem oil.  Just be sure to follow label directions 100% in terms of spraying and usage.  

Here are some Oregon State University Extension publications, articles or videos with info on tomatoes:

https://extension.oregonstate.edu/catalog/pub/ec-1333-grow-your-own-tomatoes-tomatillos

https://extension.oregonstate.edu/news/tips-growing-big-beautiful-tomatoes

For your marigolds, there are a variety of crawling type insects that might be munching on them.  Earwigs, slugs and cutworms are some possibilities.  Some organic approaches to dealing with them:  sprinkle soil around the base of the plants with diatomaceous earth (dried shells of sea diatoms, acts like little pieces of glass for crawling/soft-bodied insects); sprays such as spinosad or pyrethrins, which are generally listed for organic use.  For slugs, check out the iron-phosphate baits at a garden center as an gentle, more organic approach.  

Happy gardening, happy growing!  Cindy Brown, OSU Sherman County Extension, Moro