The leak is coming from one of the vent valves. The rubber seals on both vent valves are really cracked and they also seem a little melted? Not sure if the previous owner put something on those rubber parts and that messed them up.
I'm changing the rubber seals for sure, but I'm not sure if I need to change the valves too. Is there a way to test them? I'm also having a hard time finding them. Will the ones made for Probes fit?