Sword tail sick/sleeping?

[Vienolac]

On occasion my sword tail will sit at the bottom of the tank, kind of hidden. An not move. His top fin is clamped and he just lays in one spot,
He's one of the oldest fish I have maybe at 4-5 months roughly. But when I get closer to the tank and he notices me he will come out and swim around like nothing is fine.

In worried for him because recently I have had about 4-5 fish die on me within weeks. But all the other fish are fine now. And none seem to be sick. It's not the first time he's done it. But it always worries me.

Any ideas on why he woul be doing this?
Also my parameters are fine. Water quality is good. So I don't really understand why he does this...

 

[Morrowboarder]

My mollies do that sometimes. One has been doing it for a month. I assumed it was trying to breed. It could be stressed though. Water temp within normal range?

 

[Vienolac]

My mollies do that sometimes. One has been doing it for a month. I assumed it was trying to breed. It could be stressed though. Water temp within normal range?

Yah my temp stays at about 76-78 somewhere in there because I have Cory's and a pleco I know the corys don't like higher water temps over 80 Wich most tropical fish do enjoy.

He could be mildly stressed as I did as 3 female mollies to my tank. It's silly I see him try to show off his gonopodium to one of them, all tho they cannot cross breed.

I'll be doing a 33% water change tommorow. He is up swimming around now... He has done this a few times today. He's done it before it just started worrying me with my recent fish die off :|