Remove the gravel and rinse well. The gravel or other ornaments contain limestone or other leaching materials. Remove the offending materials. Driftwood was not properly treated and is leaching. See the driftwood section for driftwood treatments.
Bacterial blooms are common in new tanks and make the water appear milky.
Add liquid bacteria to help the good bacteria out- compete these bacteria. Bacterial blooms are often fed by excess fish food and fish wastes but many also be common in certain tap waters high in these bacteria or the foods that they like. Green water is usually caused by suspended algae. See this page and my pond algae page for information on dealing with suspended algae. Short term, do frequent large water changes until the problem subsides.