Your first problem is 'early blight' and the second problem is spider mites. These are very common problems with tomatoes. There are 2 cultural situation you need too look at:

1. Is the soil too rich? You did not say what the ratio of sand to compost/manure is. Too much compost may be part of the problem. But I sure see good tomatoes in the picture. One sign of too rich a soil is good growth but poor tomato production.

2. No cover over the soil. This is very important too cut down on splashing soil which creates wounds for fungus to enter the plant, to keep the moisture even and temperature of soil cooler, to keep water from disturbing the soil.

Tomato plants are developing brown spots on the lower foliage. This is the result of a fungus infecting the foliage causing a disease known as early blight. Early blight is an annual problem for most gardeners. It normally develops into a problem when plants have a heavy fruit set and the area has received rainfall. Spores from the fungus are spread to the lower foliage by wind and splashing rain and soil. Leaves must be wet for infection to occur. At 50 degrees F. the leaves must be wet for 12 hours for infection, but at temperatures above 59 degrees F., the length of time for infection is only 3 hours. Leaf spot development is most severe during periods of cloudy days and high humidity. To control the fungus, remove and destroy all the infected leaves so the disease is not spread from spores on the infected leaves, keep rainwater and irrigation water from splashing by keeping a layer of straw or some other mulch under the plants and keep irrigation water off foliage. A foliage applications of a fungicide must be made every 7 days until moist conditions (dew included!) no longer exist. Several applications are necessary.

 Thoroughly read and carefully follow all pesticides directions.

Go To the tomato problem solver on Aggie-Horticulture http://aggie-horticulture.tamu.edu/publications/tomatoproblemsolver/

 Spider mites are common pest problems on many plants around landscapes and gardens. Injury is caused as these insects use their sucking mouth parts to feed on the sap. The mites are on the underside of the leaves.  Damaged leaves appear as mottled or speckled on the top of the leaf caused by sucking out the chlorophyll with the sap.

Severe infestations cause leaves to discolor by producing a gray, silver or bronze appearance to the leaves. Spider mites cause serious stress to plants. Infestation is worse during dry hot weather.

Spider mites are a type of arachnid. Spider mites are tiny. Hold a white sheet of paper under an infested leaf. Tap the leaf. Watch the debris and if you see tiny red insect crawling, these are spider mites.

Large population will produce webbing. Webbing protects the mites and their eggs from natural enemies and unfavorable environmental conditions.

The most damaging spider mite is the two-spotted spider mite (Tetranychus urticae). This mite attacks a wide range of landscape plants, including many vegetables particularly tomatoes

Adequate moisture of plants during dry conditions will help limit the stress that creates the condition favorable for spider mite outbreaks. Periodic hosing of plants with a forceful jet of water can physically remove and kill many mites, as well as remove the dust that collects on foliage and interferes with mite predators. Disruption of the webbing also may delay egg laying until new webbing is produced. Sometimes, small changes where mite-susceptible plants are located or how they are watered can greatly influence their susceptibility to spider mite damage.

·       Natural enemies include small lady beetles, predatory mites, minute pirate bugs, big-eyed bugs and predatory thrips.

·       One reason that spider mites become a problem is insecticides that kill their natural predators.

Call your Extension office for the names of the fungicide and miticide they recommend.