New Endler Male Lying On Gravel

Good day,

I bought six Endler Guppy hybrids from my LFS two days ago. Five of them were active and curious from the moment I released them into my tank, while the sixth one dove down and lay on the gravel. I've seen him swim around a couple of times in the past few days, but he spends the majority of his time hiding and laying still. Is this normal for a new fish, or is there something wrong with him?
They are in a cycled 8 gallon tank, planted with lots of hiding places. Ph is 7, temp is 26.5 degrees celcius, Ammonia & Nitrite are 0 and Nitrates are 10 with low LED lighting.

Any help/advise would be most appreciated.

 

How were they acclimated to the tank? Maybe he just isn't handling the stress of the move well, or maybe he was already weak and stressed at the store and this is just a bit much for him. Is he eating?

 

Personally, I would lower the temp. to 25C. Your temp right now is at the high end of their ideal number.

 

They acclimated for about an hour, with gradual addition of tank water to the water in their bag. He ate a little today for the first time.

Varmint, I also have a Betta in there (added yesterday), won’t 25 be too low for him?

Anyway, my research said that they can cope with temps between 18-29, with the ideal being between 24-27.

Edit:
Sorry just realized I replyed three times to my own post! Forgot about the edit button!

 

Varmint, I also have a Betta in there (added yesterday), won’t 25 be too low for him?

You're right. Didn't realize you had a betta in that tank.

 

No worries, forgot to add that in my first post.

 

Have you noticed any aggression from the betta or wounds on the fish? It's possible that the betta is being a bully to him.

 

No, nothing like that. He did it even before the Betta was added to the tank. One or more of the other Endlers will lay down next to him for a while before swimming off, so he’s not being bullied by them either.

 

I had one who did this too and I finally exchanged him for another because I didn't know how much longer he would last. I had a group of four and he was the smallest but prettiest. Acclimated him to a cycled tank with no other inhabitants and same thing. Maybe the weak ones do that then?

 

I had one that did that recently.
Within a day he got worse and could barely swim; in the end I had to euthanize him.

 

As an update: three of the six are swimming and interacting with eachother and the plants in the tank, the littlest one was barely swimming yesterday and I can’t see him this morning. However, I have lost two others - one that had been weak and one that I had considered one of my more energetic ones. I have been watching them carefully and it doesn’t appear as if the Betta is chasing or harissing them. I checked my water perimeters yesterday after I found the second dead Endler and everything appeared perfect. Ammonia and Nitrite is 0, Nitrate is 25, Ph is 7.0 and temp is 26.5.