The only way to help your soil with fungal issues is to leave the area empty, cover it with black plastic and let it ‘cook’ for a season or two.
HOWEVER - you’re going to kill all of the beneficial ‘stuff’ in your soil by doing that, too - and that’s hard to get back - though it will come after a few seasons, but then you’ll be back to fungal issues again. You can’t win, LOL!
I would stick with a thick layer of mulch, making sure the beds aren’t too sloppy-wet, pruning your tomatoes up from the bottom even BEFORE you see disease issues, water plants at the base (no over-head sprinklers) and use a copper spray (it’s organic - we all have copper in us - follow application directions on the bottle) throughout the season.
Now that my tomatoes have set fruit, I will be giving the bottom 1/3 of the plants a spray with copper. We’re having a relatively dry season, so my tomato plants look fantastic. However, if we suddenly have a wet remainder of the season, all bets are off. :(
Thank you for all that great info. We had to order the copper spray as it is not sold in Michigan - got it at Walmart.com.
It should be here in a couple of days. We will definitely follow your advice next year about cutting the lower branches off and mulching we can do all that when we plant next year. Would be kind of hard to do the mulching this year. Hubby has been getting rid of lower branches and anything spotted so far and there is far better air circulation through the plants, and easier to see all the nice green tomatoes we have.