Tomato blight, like so many other pest problems here, is fungal. That's why you see the grape growers spraying so much, it's usually a fungacide to control fungal outbreaks on the grapes.
Traditionally, gardeners have used Bordeaux Mix* for fungal problems. I don't any longer consider it organic, but in my opinion, it is ok to use occassionally when you're having problems with fungus.
*Copper Sulphate & Washing Soda (many recipes on the 'net) You can get the ingredients at Saba Kimia in Denpasar.
You were right, Evelyn, about creating the conditions to encourage fungus by watering the leaves. Better you water well around the roots and keep the leaves dry. Also better to water thouroughly say twice a week (so the soil is soaked to the roots), than a light watering every day (which will keep the surface moist ie. fungal, but may keep the roots thirsty).
Finally, it's a good idea to germinate your seeds in a sterile potting mix (if your seedlings are falling over because the stem has shrivelled, it's probably fungus). Just spread your potting mix out in the hot sun for a day. You can quickly rebuild soil-life later with compost mixed with water.
Have you all got some pigeon peas in? Silvia's didn't grow well but try one seedling in a poly bag till 30-40cms then plant them out. They are fragile until established - keep weeds away from them and give them some water - so look after them until they're about 1m tall, then they should be ok.
Something to remember, in the tropics, heavy rains wash nutrients out of soils leaving them quite infertile. In nature or a well managed garden, nutrients are constantly cycled by leaf-drop, plant/animal wastes or compost & mulching, but in most modern gardens, there is little nutrient cycling and soils become infertile.
If the macro-nutrients (Nitrogen, Potassium & Phosphate) are low or missing, nothing will work. So, you need to get your maco-nutrient levels up to achieve strong plant growth. You'll do this over time with good management, but in the short term, some fertilizer will help.
Once again, it's not considered organic, but for a new project where the soils are not yet too good, I suggest an occassional (1 or 2 times/year)light application of NPK fertilizer to get your garden going. Ignore the manufacturer's advice, just a light dressing over your gardens will do. After this, concentrate on building and balancing micro-nutrients, minerals and soil carbon...
Are you preparing seedlings and sites for wet season plantings? Have you thought about stormwater drainage BEFORE the wet season? Save yourself problems later by sorting out your drainage issues now...
Silvia, I love your project, it will be one of the best examples of sustainable development in Bali - I especially like your pig system. We're looking forward to linking our Lodge guests up with your place.
Attached, a pic of Norm's new hideaway and workspace.