Merck & Co. MRK and Gilead Sciences Inc. GILD are two pharmaceutical heavyweights whose stocks tell very different stories.Rahway, New Jersey-based Merck just flashed a Death Cross, signaling potential trouble ahead. Foster City, California-based Gilead is basking in a Golden Cross, a sign of bullish momentum.Merck: Treading On Thin IceMerck, known for its diverse lineup of drugs and vaccines, is seeing its stock wobble. Despite a decent climb of 8.72% over the past year, recent technical signals are turnin ...