OP, seriously, I think you got a "bad" white pomfret. No joking. I have never had any issue with white promfret and actually they are really good if you steam them with some ginger. Make sure you check the gill if it is red. If black or white/pale, then maybe it's been frozen for months. You could have gotten one of those.
One tip: go for a smaller fishmonger (normally you will find 2, 3 in a wet market) as they generally have less variety but sell mostly fresh catch of the day. Watch out for those stalls which have lots of "Offers"