A good investment for the future would be a liquid test kit - my LFS tested my water and said it was ok to start adding fish - it actually had a trace of ammonia and nitrite and nitrates 0 (ie not cycled) so I'm glad I doubled checked!
Flashing against stuff means they're itchy - either the water is bad or they have parasites (eg ich / velvet)
plug these into your search engine and if you know your water is ok I'd research the parasites and check what is available locally treatment wise