White String Poop?

So I recently purchased 3 guppies from Pet Smart after having no fish in my tank for nearly a week now.

Prior to doing so I let it cycle, bought a new heater, checked ph, so on...

Brought the 3 home and acclimated them for a few hours while I went out for food. Came home, let them out. No issues.

Then I noticed one of the guppies was pooping something white. He was swimming in a corner by himself, and was shaking. I know from what I've read online that shaking and white poop is bad and could mean parasites :/

After he pooped it out though, he swam back to rejoin his friends and the shaking completely stopped. Now all 3 are swimming like they were, completely normal. I been closely looking at him for the past hour.

Should I be worried about him? He is a beautiful banana cream colored guppy and I really don't want to lose him.

EDIT: Noticing he is now swimming by himself, then he rejoins the others. Then he sits in one place by himself, then swims back. He has very odd behavior. The other two are swimming together and are very active, and the Banana one is floating in one spot, not really doing much.

 

It's possible that one got more stressed than the others however if it starts again I would certainly come back and look at treatment, maybe Lavamisole which kills internal parasites (worms)

 

It's possible that one got more stressed than the others however if it starts again I would certainly come back and look at treatment, maybe Lavamisole which kills internal parasites (worms)

Well I turned the light off in the aquarium and all 3 of them are bunched together sleeping now. Including the Banana one. He stopped shaking.

I'm thinking it could just be stress related. The two other guppies I hand picked at the store because they were larger. The Banana, I let the guy at the store choose, and it is a tad bit smaller than the two.

Thank you for the medicine advice, I hope I don't HAVE to buy that (kinda running low on spare funds rn), but obviously I don't want him to die so if it keeps up I will ofcourse buy it.

(Sorry I keep calling it a Banana Guppy btw, obviously not it's species. Just the best way I can describe it since I forgot it's actual species name. I think it's called a Blonde? EDIT: One of my other ones is for sure a Blonde, but this one is not..looks way lighter in coloring)

Update:

They are all sleeping, but now the Black Guppy I have is pooping too, but it's normal in color. He is ALSO shaking while pooping, then stops shaking after.

I wonder if this is just a guppy trait and I'm being paranoid due to losing fish in the past to parasites and stress.

 

may be, leave things calm down for a few days go and have a whisky good night sleep and start with a fresh head I know things like this can get to to you

 

may be, leave things calm down for a few days go and have a whisky good night sleep and start with a fresh head I know things like this can get to to you

Yeah it is getting to me. Keep worrying I'll wake up to see one of them floating :/

Hopefully not, time to sleep. I hope to see them all swimming happily in the morning. Thanks for the advice!