Guppy with a dropping tail, scratching against rocks (no white spots)

[Alexaquarium]

Okay guys, I REALLY need your help. I have been a silent reader of this site for a while. Usually only to check on peoples experiences with the fish I have but this time I have a problem.

Quick info on my tanks/fishes:
1. 60l tank with 2 adult ancistrus plecos, 4 albino corys, 6 danios, 6 bettas planted with live plants and filtrated with Aquael filter, temp. set on 25/26celsius - everything working properly and it has been up and running for about a month now with fishes
2. 60l tank with 7 guppies and a lot pleco youngsters, planted with live plants and filtrated with Eheim filter that came with the tank, temp. set on 25celsius, has been up and running for about 3 months
(I know this tank is overcrowded but I will give the plecos away to a pet store soon and I am on a hunt for a bigger tank anyways)

It all started a few days ago. It was tank number 2 that caught an outbreak. I believe it could have been ammonia. I had around 30 young plecos in free swimming (about 1,5cm long) from before but mz 2 adults have mated again and I put a breeding container with around 25 fry in to float. The next day I woke up with a murky foggy tank (water was kinda gray, almost white), there were bubbles on top and ALL my fishes were up on the surface gasping for air. I literally fell out of bed (tank is in the bedroom) and was so shocked to see all my guppies and plecos hanging up there (the fry too!!). I took out my fish bucket and with help of my partner started fishing out 60 fishes one by one. Soon we found out that one of the guppies didnt survive and the same went for 6 young plecos, the fry somehow managed to survive!!
We took out all the plants and emptied the tank completely. Spend all day washing the sand and boiling the wood and decorations...
I do not have a testing kit for the water as we always check it at the fish store but now I really wish we did so I could provide you with the much needed parameters... We will go and buy one today along with some medication.
After that another guppy has died and now another one is showing some signs of sickness. He has been swimming heavily and his tail was dropping. Pretty much all the other guppies have a problem too. They swim okay and their tails are fine but they keep rubbing their bellies at the plants/pots/wood and then quickly swimming off and repeating the process a couple of times...
There are 3 females in that I think could be pregnant. They have big bellies and a black gravid spot visible. But now I think they might have some parasites?
I did some research and found about Ich but they dont have any white spots at all. :/
The one with a dropping tail has been swimming either at the top or sitting on the bottom (not swimming around much at all unless it is feeding time).
I will try take some photos of it and maybe upload a video on youtube so I can show you more properly but until then PLEASE... please help!!!

THANK YOU!

 

[Alexaquarium]

I forgot to mention that just before my post I also did a 25% water change and he seems to be doing a little better now. Took a photo and a video.
I saw I can post videos directly on here so I will try that in this post the video. In the video at around 54th second you can also spot my other guppi scratching on the pot on the right side!! THAT is what I mentioned they have been doing... and they usually do it more than once.

 

[Delapool]

How are they doing?

The white murky water could be a bacterial bloom. Really need water specs as flashing can just be from a chemical in the water irritating them. I would agree on getting your own test kit.

Edit - if water changes are helping, a couple more won't hurt.

 

[Alexaquarium]

How are they doing?

The white murky water could be a bacterial bloom. Really need water specs as flashing can just be from a chemical in the water irritating them. I would agree on getting your own test kit.

Edit - if water changes are helping, a couple more won't hurt.

Still working on that. Trying to get a full test kit for everything instead of buying them separately. :/
I have been doing the water changes but on friday, the fish I photographed above passed away He was my oldest and had the most beautiful back fin.

However, I took out my Nikon today and snapped a few more photos which leave me hanging again... what the hell is up with my orange guy?! his side fins look so wrong HELP?!

2 others have weirdly frayed back fins

 

[Alexaquarium]

How are they doing?

The white murky water could be a bacterial bloom. Really need water specs as flashing can just be from a chemical in the water irritating them. I would agree on getting your own test kit.

Edit - if water changes are helping, a couple more won't hurt.

Still working on getting the test kit as I want to buy one that can do all the tests instead of buying different ones because it would be much more pricy :/

The fish I photographed died on Friday...

but i spotted some serious side fin problem on my orange guy and frayed back fins on two others... any ideas on what it could possibly be? :/ :/

 

[Delapool]

Could be fin rot - is the orange/yellow one losing tail colour from the end fin? Pretty quick timing though ime.

Can you take a tank water sample in to the lfs and get it tested for ph, ammonia, nitrite and nitrate? Also a sample of your tap water used for changes if you haven't already done so (let stand for 24hrs)?