This fluffy mould affects most soft fruit and is more prevalent during wet summers. Remove any plant material that is affected and ensure that the plants are sprayed with a fungicide as a precaution.
This disease is extremely common on most seedlings and causes the small plants to rot off at soil level. It is usually caused by a combination of any, or all, of the following reasons - crowding of seedlings, over watering, lack of air circulation, dirty containers and contaminated soil or contaminated water. Always sow seeds thinly in fresh sterilised compost in clean pots. Water sparingly with fresh tap water, and ensure adequate ventilation.
FROST DAMAGE at worse could kill your plants, but sometimes you get away with damage to the tenderest leaves. Unfortunatly, this is usually the head of the plant and if it has not been burnt too badly and does not die, you can hopefully continue by growing up a side shoot.
The picture here from Vegetable Heaven blogspot shows frost damage on a tomato in the greenhouse. The plants were all covered with fleece, you can still see the bubble wrap that surrounded them. Two nights of -4 was a shock in May, but I am sure that this plant will recover, especially with the tender care that this particular person shows towards her plants.
The plants wither in hot weather and pick up at night. Leaves turn yellow and brown streaks run through the stems. Spray the plants and soil with a fungicide and mulch around the stems so that new roots can form. Avoid growing tomatoes in the same soil for at least 2 years.
When tomato plants grow vigorously in mild, spring weather, the top growth often exceeds the root development. When the first few days of warm, dry summer weather hit, the plant 'realises' it has a problem and needs to increase root development. The plant tries to reduce it's leaf area by rolling leaves. The leaves curl along the length of the leaf (leaflet) in an upward fashion. It is often accompanied by a thickening of the leaf giving it a leathery texture. Interestingly, leaf roll is worse on some varieties than others.
This is just a simple case of slight overwatering, nothing to worry about, if you just ease off on the watering a little.
This problem usually applies to tomatoes. Unlike potatoes, the curling does not indicate a disease. Inward rolling of young tomato leaves is usually taken as a good sign if the leaves are dark green. The rolling of older leaves is a sign that too much foliage has been removed from the plant or a wide variation of temperatures. The plant shown here looks like it has taken up excessive nutrients, which could be in the compost. It will settle down and should grow out of this.
Magnesium is one of the major constituents of chlorophyll. Signs are a paling of the leaf between the veins, which eventually turn brown and die. It most often occurs in very acid or very limey soils. Check pH and rectify. An application of Epsom salts applied at the rate of 2oz per gallon of water and sprayed on the foliage at fortnightly intervals will also help.
This causes yellow speckles on the leaves, which may tend to turn up. Very sandy and very alkaline soils may be deficient in Manganese. In severe cases apply a foliar feed of Manganese Sulphate at the rate of 2oz per 5 gallons of water.