Is This Ich?

Bear with me; I'm pretty new to this. Set up 100 litre tropical tank just over 6 weeks ago, followed fishless cycle religiously, waited for 0 NH3, 0 NO2, got NO3 to <20, ensured stability for a week, then added 6 white skirt tetras, a week later 6 corys, a week later 2 amino shrimp; all healthy and happy with daily water checks (API liquid tests) saying 0 NH3, 0 NO2 and partial w/c keeping NO3 <20ppm. pH is 7.6, temp 24C. All going very well and all are feeding and getting on well. This evening, one of the two female platys is rubbing against gravel and plants occasionally (believe it's called flashing) and dorsal fin is close to body (believe it's called clamped). Still feeding well, pooping well, and socialising with the others. The other female platy and all other fish/shrimp doing very well; no clamping or flashing. After researching on here, I read it could be ich. Then I convinced myself that I could see a single white spot on her black tail fin. Should I take action now (temperature, salt, treatment?) or see what happens for a day or two?

ammonia can cause fish to flash...did you give the testing kit bottles a good shake before use, also if it is ich then heat the tank to 30 for 10 days, but raise the temp to 30 over a few hours to a whole day, ie...a degree every hr or 2....

can you post a pic?

salt is to be used carefully with cory...do research that!

Is the spot on the fin the size of a grain of salt?

Very confident with test results, know to shake particularly nitrate bottle 2 for a couple of minutes, very diligent with testing. The spot is not particularly well defined (not sharp edges), and maybe a little bigger than a grain of salt. I'll try to get a pic tomorrow and post on here for expert opinion. Here's a pic of the said platy just after adding to the tank; no clamped dorsal fin but possible the white tail blemish even then.....

Does the spot on the tail look a greyish white colour.
Does the spot have any red, pink in the centre of the spot, or outside of the spot.

Pics of whitespot

No, it doesn't look that those. They look as if they've been sprinkled, this looks, if anything, like a small lighter pigment (from what I could remember when the lights were on earlier this evening). Just looked now, lights off, and she's calmly drifting around near the gravel (still clamped dorsal fin), with most of the others (except the corys, who never stop!). But the with the tank lights off I couldn't see any spots or even the light tail pigment area. Pretty certain what I saw earlier was nothing like the pics above show though. Will check again and photograph tomorrow, thanks for the help so far!

Anymore spots or flashing?

She may have just had an itch

Did you do a water change lately? I use stress coat when i do i waterchange and my corys used to flash, someone on here suggested i used the recommended dose, i used to double dose in case of copper was still leaching from my tank, so now i use the proper dose and my fish dont flash....just an idea......

No spots; don't think the slight discolouration in the centre of the tail fin is ich. The apparent triangle of "spots" in front of the pectoral is just water bubbles floating around! Haven't noticed any flashing this evening so far, still feeding well (and poking a you can see), although a bit more skittish than the other platy, and dorsal fin is still clamped, maybe not as much as yesterday though. Tail fin was also clamped yesterday, but has relaxed now. Water parameters tested ok; pH 7.8, NH3 0ppm, NO2 0ppm, NO3 10ppm. Temp 26C. Last partial w/c was three days ago, I don't use Stress Coat, just correct temperature tap water treated with Aquasafe. Will keep an eye on her and report back if anything changes!
Thanks.

Thank you for the update.
Good Luck.

Platy update - no spots and not noticing any flashing; slightly more jumpy behaviour than the other female platy and still a semi-clamped dorsal fin. Guess she's just just found the move more stressful and needs some time to calm and feel comfortable. No issues with any other tank mates. I have noticed this though - a huge amount more poo than any of the other fish from this red platy! Could that give any clue as to what is distressing her?

What colour is the fish waste please?
Check her anus to see if it looks enlarged, or red and inflamed.

Waste is fairly solid, inch long tube before it breaks off after a few minutes, light grey and dark grey. Anus doesn't look abnormal (compared to the other platy) or inflamed.

Grey/brown, definite patches of light and dark colour, difficult to tell.....since last weekend she's been fed tropical flakes and a couple of freeze dried daphnia, before that who knows at the store. But the other platy I bought at the same time from the same tank is doing great.

Try feeding your fish some peas.
If no improvement don't hesitate to post back on your thread.

Drop a few frozen garden peas into a jug of boiling water for a few minutes.
Let the peas cool down. Pop out of shell and cut into small pieces and then feed to your fish.
Remove uneaten peas after a few hours.

Good news; I didn't do anything special, just maintained water checks and changes to keep nitrate around 10ppm, and the platy is now "normal"; fins open and much calmer. The only thing I have done is rinsed filter sponge in used water, and, inadvertently, slightly reduced the flow rate from the pump. Probably a coincidence, and just took a while for her to acclimatise to her new tank and tank mates, but could she have been unhappy with too much current?

Anyway, all good, thanks for the help!