My friend just gave me a KRK Rokit 8 2nd Gen studio monitor for free. He said it's volume output has gone down significantly since he got it. After searching online for a bit, I thought the problem might be a faulty capacitor, so took off the back panel and had a look around. Everything looks pretty normal to my eyes, but I'm A.) Not sure what the black substance on a lot of the capacitors is. B.) Not sure if this bulge on this particular capacitor indicates that it has broken. Could you guys help me see what's going on in here? Thanks a lot!