Soaker hoses do go above the dirt but below the mulch. If you haven't mulched, I recommend doing so...it will help them retain water. The hoses can get clogged sometimes, too. Never prune a water stressed plant...it can kill it. Are the leaves turning yellow, or are they brown and dry? If yellow, it is probably a nutrient deficiency, most possibly iron, and a good dose of iron rich fertilizer can help. If the leaves are brown and dry, then it's a water issue, and it will depend on the severity as to whether giving it more water will correct it or if it's too late.