My suggestion would be reducing stress to your fish, something caused this, ich isnt random, its the result of something i.e poor water, flucuating temp, bullying, bad food etc and if you dont figure out whatever variable is out of whack then your likely to be going at it for some time, spring is here and your tap water mite have some changes in it that your fish arent used to, like more chloram/chlor/calcium etc (assuming you do WEEKLY changes) it could even be stray current which is why a grounding probe is a good idea!
Dont bump too 90 imo. 84-86 is a good start add your salt (let it dissolve in bucket first!) And turn the lites off for a few days and let him rest and rejuvinate, basically just dont stress him w/ constant movement!!
you never mentioned water params, yea you said the waters fine but ive heard that a million times then i hear is .5ppm of ammonia bad?? Lol
#1 S. Vettel