Discus Died suddenly, any ideas of cause?

[lpsouth1978]

Hello all. I had one of my discus die mysteriously today. When I fed this morning before leaving for work all of the fish looked great and ate excitedly. The only exception was the fish in question. It stayed in the back of the tank among the branches, but seemed ok otherwise. I did not think much of it at the time and figured I would check it out after work tonight. About an hour later I got a text with a picture of the fish on the bottom of the tank dead. I have no idea what killed it as there were no outward signs of any illness. Please help me with any thoughts, so I can avoid this happening to any other fish. Here is info on the tank:

Waterbox 230.6
Ammonia - 0
Nitrite - 0
Nitrate - 5 to 10
pH - 5.7
kH - 1
GH - 2
Temp - 83

I do daily 40 gallon water changes with RO water treated with RO right and aged 24 hrs. I feed a homemade beefheart mix 3-5 times a day. There are (were) 17 discus, and there are about 12 Sterbii cory's and 5 GBR's. There were 2 spawning pairs and the fish that died was the female in one of the pairs. All fish have been in the tank for at least 3 months and there have been no new additions.

Please let me know your thoughts and if I left anything out. I would really like to keep this from happening to any other fish if I can.

Here is the picture that was texted to me.
https://live.staticflickr.com/65535/48537147647_8c0c9bc30b_o.jpg (https://flic.kr/p/2gX4yZe)2019-08-14_09-02-50 (https://flic.kr/p/2gX4yZe) by Lyle Southard (https://www.flickr.com/photos/166227805@N05/), on Flickr

[jeep]

It doesn't look like it was sick and your set-up seems fine. It doesn't look much like an intestinal blockage. Could it have possibly hit the tank wall or something? Sometimes it just happens :confused:

[lpsouth1978]

I don't know of anything happening to it. As I said, it seemed ok when I left this morning, then this. Hopefully it is just a freak accident and I have nothing to worry about with the rest of the fish.

[LizStreithorst]

I had an adult Discus die suddenly once. It happens rarely, but I know from experience that It does in fact happen. Sorry for your loss.

[lpsouth1978]

Thanks Liz.

[danotaylor]

I had a perfectly healthy red melon crack it's head badly on a blunt rock when it got spooked. It was kinda concussed for a day and went from top of pecking order to bottom in hours, stopped eating, developed a sore on its side where it was injured by another discus, 2 days later dead...1 of nature's curve balls
Sorry for your loss Lyle :cry: