Good for you that you put together a raised bed. Raised beds are much like container planting, they need water everyday because they dry out quickly if you don't have an irrigation system laying on top of the soil. Water is likely why things didn't survive. You also should have mulch of 3 in on top of the soil so the water is held in longer, and the sun doesn't super heat the soil which can get as high as 108* easily and will cook the root system. If you are trying to put bigger plants with a more expansive root system in like roses ( they need at least 24" on soil to grow down into). The white on top of your soil is the collection of salts, lime, and calcium that is naturally in our water. We have very hard water with lots of minerals. You likely believe you have a fungus, not true, it all minerals. You need to water thoroughly and deeply to move the salts and some of the minerals through the soil. You would be helped by buying a moisture sensor at some place like Star Nursery so you can check the soil to make sure it is really getting thoroughly damp. The soils you may have used may not hold water well. You may need to add some additional soils that hold water better. You can check for that at Star or Plant World. Also you can visit the U of N - Reno, Coop Ext Las Vegas at Windmill and the 215 see raised beds that successfully grow veggies and many other plants. There are Master Gardeners there M - F from 8 - 5 and if you watch the newspaper, you will find many classes available to you at the Ext.