Coccidiosis doesn't cause urinary problems in goats. Causes the squirts and failure to thrive. Wouldn't expect it to kill an 8 month old goat. Male goats are especially bad about urolithiasis blocking them up leading renal failure. Metabolic neuroligical signs can occur as well late in the disease. Very common in goats feed high protein concentrate grain diets. If that's all they've been eating I'd highly suspect they were blocked based on what you've said. They've got to have roughage as well, and access to plenty of clean water.