Why would my angels be doing this?

Ok..I have a well established 220 that is housing 4 angels, 6 clown loaches, 2 festivums, 2 gold severums, and 2 uaru, and 4 clown plecos. About 4 months ago redone the tank, I didnt break it down, all I did was more or less change the fish, trading all the smaller tropicals I had for some of these cichlids. I have had the fish for at least 4 months, they are growing and doing just fine. my question is, I noticed the other night one of my angels, was at the top of the tank , kind of riding the current from the filters. He was eating fine, still responds when I walk up to the tank and everything. No clamped fins, no signs of nothing.He isnt breathing hard or nothing.Then, yesterday, i noticed another angel had joined him. By last night a third angel had joined the other two. Today all four are there. Like I said, it makes me think of salmon running upstream.They are riding in the faster water. They are eating fine, everything. I have tested my water over and over, my ammonia is 0 , nitrite 0, and my nitrates are 0. My ph is about 6.8, the water is soft. I use peat to soften and condition the water. Any ideas on what they might be doing? LikeI said they are not breathing hard. And they kind of hold their head upwards, just a bit.Also, there is no aggression against them, and the other fish arent doing this

Yeah I have some local native aquatic plants in it. As for aggression, there is none. none of the other fish even acknowledge the angels, they have free run, no stress. Heck they are hand tame, I can stick my fingers in and even my loaches come up nibbling. I have never had this happen. I had angels in with the same species(plus a H temporalis) in my 90 years back, those angels even bred in the community tank. I have had these angels long enough to know they are parasite free, I think. I have had them about 3 1/2 - 4 months. They grew from quarter size to silver dollar size. I am looking at them right now. Two now have their tails a little clamped. No new fish have been introduced since it was redone. Also no plants. I have not changed the food, I have not changed my water conditoners. I am just stumped. :help: