I have a small yellow tang in a 75 gallon tank. Is that large enough? He's about 2 inches. I've had him for about a month and a half (he was in QT and then in my tank for about a week now). He seems to be VERY skinny although he eats like a pig. He also seems to be getting light orange markings on his face and some slightly darker dots. Is this pore rot or whatever it's called? If so, or if not, what should I do? Thanks.