Deck rot
I've had/have similar problems. People here have told me the brown goo is from rotting plywood in the deck core. The only time I had the colored streaks was following a large coffee spill on deck (right on the leaky side). No brown before or after that. Still, the leaks were there at the stanchions and bow pulpit. A PO thought the leak was at the hull/deck joint. They caulked the bottom edge of the rubrail, so that it now holds water and may have created a leak at that point. All in all, my leaks are not severe yet. Check the chainplates too. If you are industrious and haven't done so yet, add the backing plate kits for the stanchions and chainplates and rebed everything at that time.