Thanks, but I have read to never add oil to soil though for this purpose it would help the soda to stick to the plant. However, what I am seeing looks more like Fusarium Wilt (Water the plant to see if the wilting persists. If you are sure it is fungal wilt, the best thing to do is destroy the plant.)
Fusarium Wilt Fusarium wilt is wilt that occurs quickly and watering doesn’t help. The plant will look healthy, and then they start to wilt. It might only affect half the plant at first, but will quickly spread to the whole plant and quickly kill it. It’s caused by the fungus Fusarium oxysporum f.sp. lycopersici and it can survive in the soil over the winter. This nasty fungus is best prevented by crop rotation and using an organic bio-fungicide such as Mycostop.
Less likely is Early blight, "large black spots surrounded by wide areas of yellow spots on tomato plant leaves. The leaves will have a characteristic pattern described as an oyster shell or bullseye."
Fusarium and Verticillium Wilt
Fusarium and Verticillium wilt are caused by fungi in the soil that enters your tomato plants through the tender, young roots. The fungi then plugs the vessels that gets water from the roots to the stems. As you can imagine, your plants will begin to decay due to lack of water flow. On sunny days your plants will appear wilted, then appear to recover during the night (wilting may first appear in the lower or upper leaves of the plant, causing discoloration). Eventually leaves will die backward from the leaf tips as the wilting spreads throughout the entire tomato plant. Fusarium wilt is the most common tomato plant disease in regions with warm weather regions as well as in cooler regions during the periods of warmest weather.
To avoid these tomato plant wilt diseases, make a point to plant tomatoes bred for disease resistance (Heirloom tomato varieties in particular not bred to withstand these types of diseases are particularly susceptible to tomato wilt). Look for plants labeled with an "F," "FF," or "FFF" (for Fusarium variations), or with a "V" (for Verticillium). Be sure not to overwater your tomato plants--a wilted plant does not mean it needs more water, so check the soil. If it's dry, then go ahead and water.
If your tomato plants are affected by any of these wilt diseases, extract and destroy them. Do NOT place them in your compost pile. Do not plant tomatoes, peppers, potatoes, or eggplants in affected soil for four to six years because of residual fungus that remains in the soil (corn and beans won't be affected). Keep affected soil well weeded as their roots continue feeding on the fungi. - https://maggiesfarmproducts.com/blogs/tips-tricks/tomato-diseases
Then there is, "when older leaves on tomato plants turn yellow while the veins remain green, the macronutrient may be just what the doctor ordered. Mottled yellow leaves that eventually turn brown and drop off are a sign of magnesium deficiency in tomatoes. Applying a foliar spray of 1 tablespoon of Epsom salts per foot of height of the tomato plants dissolved in 1 gallon of water can help alleviate symptoms. - https://homeguides.sfgate.com/can-epsom-salt-used-fight-tomato-blight-98447.html
Other info on Early Blight beside the common measures (spacing, much, drip watering, amputation of affected, sanitizing equipment, etc.):
Seek out tomato varieties that have resistance or tolerance to early blight, indicated by the capital letter “A” (for Alternaria) after the variety name on plant tags or seed packet descriptions. A few varieties to look for include ‘Iron Lady’, ‘Jasper’, ‘Mountain Magic’ and ‘Big Beef’.
Products recommended for control of early blight include Serenade®, sulfur or copper based fungicides, potassium bicarbonate and fungicides containing chlorothalonil. All are considered organic except chlorothalonil. - http://masterofhort.com/tag/early-blight/
A good and more extensive page on blights and w/ lists on resistant toms is https://hgic.clemson.edu/factsheet/tomato-diseases-disorders/
Early Blight is something that plagues me in wet seasons such as this one.
But, rotating crops/beds and growing blight-resistant varieties helps A LOT, as does a spray of copper when you’re doing that first pruning of the season.
I couldn’t get to any of that this season as it rained every 18 hours or so for weeks on end.
It is what it is. Some years you just have to take your losses and move on, LOL!
I am SO GLAD that I know how to get to the grocery store if need be. ;)