Welcome to the forum!
Could be wrong, I'm not professional, but looks like ich.
DON'T FOLLOW THESE INSTRUCTIONS YET, because mistreating a fish can make it worse. Wait for some more confirmations and
then try this.
First- (answer this ASAP)
How long has the tank been set up for?
How long have they had the spots for?
How many have it?
Do they/it have any other symptoms?
Have you added anything to the tank in the 2 weeks before this started?
What else is in the tank?
Water parameters? (Ammonia, Nitrite, Nitrate, pH, etc. )
How big is the tank? (probably not relevant but give it anyways)
Something I found on an old post by
@Colin_T , (that I edited slightly to make it fit this context)
------------------
To treat white spot (ich), raise the water temperature to 30C (86F) and keep it there for 2 weeks, or at least 1 week after all the spots have gone.
Before raising the temperature, do the following-
Wipe the inside of the glass down with a clean fish sponge. This removes the biofilm on the glass and the biofilm will contain lots of harmful bacteria, fungus, protozoans and various other microscopic life forms.
Do a 75-80% water change and gravel clean the substrate. The water change and gravel cleaning will reduce the number of disease organisms in the water.
Make sure any new water is free of chlorine/ chloramine before it is added to the tank.
Clean the filter if it hasn't been done in the last 2 weeks. However, if the filter is less than 6 weeks old, do not clean it. Wash the filter materials/ media in a bucket of tank water and re-use the media. Tip the bucket of dirty water on the garden/ lawn. Cleaning the filter means less gunk and cleaner water with fewer pathogens so any medication (if needed) will work more effectively on the fish.
Increase surface turbulence/ aeration to maximise the dissolved oxygen in the water.
------------------
If the heater struggles to hold the temperature at 30C (86F), tape some 1-2 inch thick sheets of polystyrene foam to the back and sides of the tank (on the outside). If you haven't got foam, put a towel around the back and sides of the tank but make sure it doesn't touch the water or come in contact with the light.
___________________________________
Back to me, I also am aware of a product called 'Ich X' or something that others may have experience with, however cannot vouch for it as I've never (yet) had a problem with ich.
If it's the only thing that has it, would recommend quarantining it if possible.
Good luck!
PPJ