Everything is dying

[opalust]

So I had a rocky start to my freshwater shrimp tank, but after a while I got the hang of it. Now, seemingly out of the blue, EVERYTHING is dying. 

I started out (once I smoothed out my issues) with 2 Ghost Shrimp, 2 Amano's, 2 Red Cherries, and 2 Orange Bs. I also have two Cory Cats in the tank, which is a planted ten gallon with filter and heater. 
First, one of the Ghost Shrimp died in the molting process, so I started adding Iodide to the tank, three times a day (because I have a carbon filter). Everything is good, we even had little Amano babies running around, so I put a sponge over my filter so there were no more losses in the baby department.
SO about a week ago, the remaining Ghost shrimp disappeared, and since the tank is WELL planted, I had a hard time finding its body. Then, BOTH of my Orange Bs.... mysteriously vanished. Then one of my Red Cherry Shrimp (which may still be in the tank, but I have no real way of knowing right now). 
Yesterday I took out every plant and though I found the dead Ghost Shrimp, there is no evidence that I even HAD Orange Bs in the tank. No bodies, no shells, nothing. Just gone. 
I did a HUGE water change (about 60%), added Prime, tested the water, and all my levels were good. PH was slightly low, but it's always been that way without any problems.
This morning I wake up to a dead Amano, which have been my most durable shrimp yet. All the babies are dead and gone. All I have now is one Amano, and one Red Cherry Shrimp (to my knowledge). Tested the water this morning and the parameters were still the exact same as yesterday. Nitrite and Nitrates are zero, I put in a tab to raise the PH .5, so......
THE ONLY change that I have made since this tragedy has begun is lower the heater temp to about 72-75. I had it set before at 80 degrees, although the water was always about room temp. Could that really be killing my shrimp off like that? I don't have any clue what's going on..

EDIT: Not only this, but the shrimp have been.... not moving. Not interested in food, just kind of sitting there. This is also after I lowered the temperature, and before everything started dying and disappearing. They are still doing this.

** I apologize if this is in the wrong location, I'm just panicking right now. I do not want to lose any more of my shrimp.

Edited April 8, 2016 by opalust

[Disciple]

Welcome to SKF @opalust

Sorry to hear of your troubles. I think you did the right thing lowering the temp. 73 to 75 is a good temp. 80 is not too bad but it could cause some issues.

Doing a 60% water change could stress the shrimp if you do it too fast. You also said you added prime I assume this was before you put the water into the tank?

Can you check the Tds, Gh and Kh of your tank water? How long have you had your tank running for?

[jayc]

Opalust, sorry to hear the news.  Hopefully we can stop further deaths. 

Disciple is right,  we need GH, KH and TDS readings of your water parameters.  Moulting issues can be attributed to high levels of GH, KH &TDS. 

Do you add any minerals into the tank as supplements?If the tank has been running for 6 - 8 months with no added minerals, it can be completely stripped of minerals needed for proper moulting. Shrimps use up a lot of Calcium for forming their exoskeleton. Magnesium in the right amounts is need for calcium absorption. Potassium is another major mineral required for health benefits. 

A picture of the tank might help us with the diagnosis as well.  We might spot potential issues.

Hopefully you can give us a reply to those questions.