Can anyone explain the drunk/ stoned like behavior of my marble-gold angelfish?

Hi guys,
I was wondering if anyone could explain this behavior to me.

I have a couple of marble-gold angelfish in my tank. It's a long story: (http://www.aquariacentral.com/forums/showthread.php?t=211492&highlight)
But to cut it short, I got suckered into a 16G tank 3 weeks ago and the seller dumped 14 fish into it at the beginning itself without cycling it. 2 of them died and I managed to return some of the fish and now I am having to cycle the tank with 2 angelfish, 2 swordtail tangerines, one pleco and 2 silver dollars inside it.

As a result, I have to do 25% water changes daily to compensate for the ammonia/nitrite production. Since some of them also had an Ich infection in the first week I'm maintaining the temp at 84 degF and 3 tsp sea salt/ gallon for 2 weeks and this has gotten rid of the Ich.

Yesterday, after I added the salt solution after a water change (to compensate for the salt removed by the water-removal), one of the marble-gold angels looked like he had been stunned by something. He suddenly went quiet (unlike the alert self he usually is) then he began to careen towards one side like a drunken person who loses his balance. He would then try to right himself and then again do the same. Throughout he seemed to be looking at the surface of the water.

Normally on waving my hand across the glass, both the angelfish follow it. This guy did not do so. He just stayed in his place and fluttered his fins. Also, the movement of his fins did not correspond to his movement, i.e. he would remain in the same place inspite of vigorously moving his fins. I have been observing our fish closely and now I have an approximate idea how much each fish moves his fins to move around. I found this fin movement rather abnormal.

After a few minutes, the other fish began to nip at his tail and side of the body. The shocking thing was that he did not even try to defend himself! As if he didn't care at all. Like he was stoned or something.

Fearing something wrong, I transferred him to a quarantine tank along with a goldfish. Within seconds he seemed to regain his senses and began to swim around normally. He's fine today. Only, he has not yet regained his usual voracious appetite.

Can anyone tell me what this is all about? Was it the addition of the salt solution that did it? Or something else...
Anything else I should be doing?

I am an absolute newbie so please forgive my ignorance. Any feedback would be most appreciated...

Thanks. Could it be 'shimmying'

Thanks for all your replies guys!

The way I add salt is by dissolving it completely in a mug of aquarium water and letting it run down one of the side walls of the tank so it 'slowly' enters the tank water. But as I was looking down the top of the tank at that time, it is possible that the angelfish thought that I was dropping fish-feed into the tank and rushed towards it as he always does, and in consequence, either swallowed it, or got drenched by it.

I also admit that the temperature of the water could be lower than that in the tank since I don't have an additional heater to heat up the water to the same temperature as the tank water.

I was also concurrently hunting for some reason on the Internet. Some of the articles say that his symptoms seem to match something called 'Shimmying'. Could it be this entity?
I also read that Shimmying can be caused by sudden change in water chemistry. And I guess getting drenched by a cold salt solution would constitute a sudden change in water chemistry! Aagghh! My bad....

And yes excuzzzeme, now that you mention it, I think I should tone down the salt quantity a bit to about 2 tsp/gallon. It's just that we were so frightened by the Ich bug, we kinda overreacted with the treatment :

Now do I do anything active about it or just let him get over it on his own?

Thanks again :clap:

Update.
It was probably shimmying due to a sudden change in water chemistry.
After a couple of days in quarantine, I put him back in the main tank. He's perfectly all-right now.