Which tomatoes? I would give you a piece of my thinking, but without further elaboration, I feel I may be stepping on unknown information(going in circles), which is the name of the game, since that is life.

Take care,
Travis

What type of soil condition do you have,within the 3 month tomato growing process? Better yet, in average conditions, over the thirty years, have you noticed any visual change of your topsoil?

Try getting a soil test done .
You may speed up vigor with an addition of Epsom Salts mixed in with water.
Are th raised bed draining water freely ?

What do the plants look like? Pictures would be great.

I'm definitely not an expert, but here's the little mental check list that I usually start going through when my plants don't look happy: 1) Is it a nutrient deficiency or excess? (what have I been feeding my plants, or not feeding them lately?) 2) when was the last time I checked my soil's pH?, 3)Is the soil excessively wet or dry?, 4)Is the air too hot, or too much sun - (in spite of tomatoes reputation for loving heat & sun, I've noticed that, even here in the NE, mine sometimes really suffer in the July heat and do better with some shade cloth), 5) Is the soil too hot? (same reasoning as number 4 - I've noticed that in raised beds, the soil can get hot if there's not enough mulch or plant cover), 6) Am I mulching with something that might not be agreeing with them?, 7) What am I seeing on the plants: spots on leaves?, wilting?, stunting?, too pale?, flowering but no fruit?, leaves but no flowers? insect damage, etc.)(then, consult the internet for possible diagnoses)..... 8)Have I done any foliar feeding lately? - sometimes, when my plants don't seem to be getting what they need out of the soil, some foliar feeding can give them the boost they need.....

It's probably not too helpful, but here's hoping that it is....

Whoops - just re-read your post & realized that you've been growing heirlooms for years and must have thought about all these things. For blight, in spite of this being controversial, I've actually had success with milk and water foliar sprays (though sometimes I use yoghurt), especially if I'm consistent. I've also mixed it with some rock dust (adzum, which I think is similar to azomite) - it clogs the sprayer some, but I think it boosts the effectiveness. I'm becoming a fan of rock dust. And Epsom salt as the poster above recommended. Whatever's left of whatever I'm mixing in the sprayer gets dumped in the soil.

Sometimes I think that global warming might be making the incidence of fungal & other diseases more prevalent in northern areas than before, so maybe that's what you're seeing.

One more thing: has there been any change in the water you're using?

Try growing them somewhere else in other soil not in your raised beds. Maybe you got some walnut leaves in your mulch or rotten hay sprayed with Grazon.

Do you rotate your crops?

Sure feel your pain but here's a thought -

Try growing a couple of hybrids between a couple of heirlooms just to see if they have different results.

As an aside, ten years ago I started adding a handful of bonemeal in each planting hole and that did wonders in terms of correcting disease problems.

Good luck !

In my opinion, considering that Global Warming is still a debate, not fact, would bring me to the conclusion that would not be a factor.

Science I believe in, but not science that proclaims something that involves only a tiny,small, and short period of study,which it is. We are dealing with incomplete information and underestimating Earth's ability to correct itself.

Do not believe man over the Earth. As far as I see it, Earth will take care of it.

Take care,
Travis

Has your area been trending to a more moist environment, with much more frequent rainfall.