Hm, could've been a parasitical issue, or internal parasite issue, too. It's not always food that causes bloating. Like dropsy, you see bloating, but obviously you aren't feeding him. Or food-lag as well.
Also, to iamntbatman, I believe pineconing is a symptom that heavily indicates dropsy, and is a very common symptom, however is not present in 100% cases of dropsy. Sometimes it's just heavy bloating, or who knows what else. We'll never know for sure, though.