Fish flashing and not sure what to do.

[PuddleJumper]

Recently I just got 2 female dalmatian mollies and 2 female red wag swords in my 75 gal community tank. Fulval fx4 no carbon and planted tank. Has a colony of Guppies and a decent size common Pleco. I did not realize it was bad at first but they came into the tank and where flashing. Looked it up and found it could be a sign that they brought something into the tank. I have the chemistry seems good low nitrates, no nitrites, no ammonia, and the ph is a little higher than I try to keep it at an 8 but have been working on that. Recently notice a guppy or two starting to flash as well. What would you all recommend? I have been keeping my eye out for white spots for ick and have not seen any indication of that. I have noticed on one of the mollies, seen in attached, that it has a few gold spots so I'm concerned about velvet but no other indications of that but they all seem to be eating not and not having anything else wrong with them. Would it be safe to use seachem paraguard as a just in case measure? Thanks

 

[Autumnsky]

I wonder if you rinsed out the media in the canister filter using tap water, replaced sponges or padding?

Do a test for ammonia, nitrites and nitrates.

Watch for little white salt looking specks, Ich.

Do a couple of water changes to dilute the probable unsafe water parameters.

Do you use Prime water conditioner? If not does the one you are using neutralize the unsafe water - ammonia, nitrite and nitrate.

 

[PuddleJumper]

I wonder if you rinsed out the media in the canister filter using tap water, replaced sponges or padding?

Do a test for ammonia, nitrites and nitrates.

Watch for little white salt looking specks, Ich.

Do a couple of water changes to dilute the probable unsafe water parameters.

Do you use Prime water conditioner? If not does the one you are using neutralize the unsafe water - ammonia, nitrite and nitrate.

Thanks for responding. So I just checked all parameters of my tank and there is 0 ppm of ammonia, 0 ppm of nitrites 20 ppm of nitrates with a ph of around 7.6. I have rinsed out my filter media with tap water in the past but I have tested it and they dont put chlorine in my tap water. I do treat all my water with prime. I also have been dosing a little bit of prime just to be safe. I also have started to dose tank with seachem paraguard. I have not seen any white specks either.