something spooking my fish?

A few minutes ago I went out into the hall to check on my 55 gallon tank. The bleeding heart tetras were all acting crazy scared, kind of the way they'd act if I'd been chasing them with a net, or if there were a bully in the tank. They were swimming into the corners of the tank, pushing into the gravel, and all hiding in the plants.

There are 8 bleeding hearts, some of which I've had for quite a while. No new animals in the tank with the exception of some amano shrimp I added last week which may or may not still be in there. There are also 4 cories and 3 black skirt tetras, and all of those other fish seem to be acting normal.

I tested my pH and saw that it might have been down as low as 6.8. That is down from the last time I checked it. I've been running 4 bottles of DIY CO2 for about a week. Thinking maybe it's a problem of too much CO2, I pulled out the line from one of the bottles and added an air stone.

I haven't tested my other params yet. I did a water change a week and a half ago. Just started adding dry ferts to it this two days ago, based on EI dosing amounts. Added a dose this morning about 2 hours or so ago.

Any thoughts on what might cause this? I'll be doing more param testing a little later.

Update:
The fish gradually calmed down. I removed the air bubbler after reading GoldLenny's comment above. i decided they weren't really acting like it was a breathing problem. I didn't do a water change, though. Over the course of the past couple of hours I would look out at them and see that they were acting normal, but then if I'd stand up to walk out there they'd all scramble into a group and hover in the plants. So something about me moving is spooking them in a way that I've never seen before. But a little while ago I did some work moving plants around, and they seemed calm and fine with that. I'm wondering if there's something going on with the lighting and the shadow I cast... I have no idea.

Also I fed the fish, and they were very into that. Except now it seems as if there's one of the bleeding hearts, one of the biggest/oldest, who isn't seeing very well. I think his eyes look a little cloudy, and I think he was having trouble finding food. I think that is new.

The electrical leakage idea crossed my mind; and then of course I started playing around with plants without unplugging anything. That takes the kind of smarts I'm proud of. But nothing happened, and I didn't notice anything that would indicate that there is an electrical leak.

Thanks for the help. Hopefully there's nothing serious going on.

My temperature looks okay, the tank's in the basement and we have the A/C on all the time.

I have a blackout period for an hour every afternoon, and that just ended. I went to check out the tank when the lights came on, and all of the bleeding hearts were okay except the one, which was floating down in a back corner of the tank. It's the one with a cloudy eye - looks like just the one eye is sort of cloudy. I watched for a few minutes, and a black skirt wandered over into that area, and dropped down into the corner, and that sent the bleeding heart kind of shooting up recklessly around the tank, and all of the others sort of huddled and headed for the plants again.

I think if there is such a thing that bleeding heart is the alpha of the school, and they're all taking the cue from it. And I think it's going blind and so things are spooking it, like my movement blocking the light from my office, and some of the other fish in the tank.

I am wondering if it ate a dose of powdered ferts and that caused this. The first day I dosed I did it with the lights on, and some of the fish swam to the powder and at least one of the bleeding hearts sampled and then spit out some of the stuff. I have no idea, that could be just a coincidence. What things can cause a cloudy eye?

They're at it again. Now it looks like at least 2 of the larger ones have a cloudy eye.