A: It’s a question of nutrition.
Raised garden soil blends typically have lots of aged pine bark and compost in the mix, which is perfectly fine. But these materials leech nitrogen from the soil in order to break down, and a raised garden is usually watered harder than a garden in-ground because you must do so to keep your plants happy. The nitrogen which isn’t being locked up by the composting woody bits is washing out the bottom of your bed. Plants require nitrogen for leafy, green growth – so your leaves aren’t green, nor are they growing well.
It’s a simple fix. Fertilize harder, and with more nitrogen. You’ll have results in a gratifyingly short period of time. Apply half a pound of Hi-Yield Ammonium Sulfate evenly across each 100 square feet of garden bed, and add a teaspoon of the same fertilizer around each vegetable start individually. Add more monthly to support your plants’ growth. Water immediately after application.