Posted: 12/07/2013 at 09:02
A couple of things, bookmonster.
First, spraying against fungal problems has to be preventive - ie, spray before the fungal spores arrive. Once they're in situ, with symptoms showing, spraying is a waste of time. All you can do is remove the affected leaves to try to minimise the spores' spread.
Second, your spray recipe isn't going to help even if sprayed preventively. It's claimed by some that bicarb can alter the pH of the leaf surface to create an environment unsympathetic to fungal spores but the evidence is entirely anecdotal. There's no scientific evidence to support the claims.
About the only available* spray that has been proved scientifically to help against fungal problems - if sprayed preventively - is one of the copper sulphate products. They're organic and they used to be every tomato grower's best friend until concerns were raised about (a) copper being a metal capable of building up in the soil; and (b) its impact on foraging insect life.
*The very best spray against fungal problems is a chemical that, to my knowledge, isn't available to the domestic market in the UK. Unlike in the US where it's widely available and very widely used even by many organic growers such is the product's otherwise benign properties and qualities.
Unfortunately this site's photo software is playing up again so I can't get a good, close look at your plants. Any chance of some closer photos?
The second photo seems to show a fungal problem. The pale leaf colour, though, could be a nutrition issue. Are you using commercial potting mix or home compost?