Your post is very vague to be honest.
First of all, I would like to know how long has your tank been established. What are your water parameters (ammonia, nitrite and nitrate)? What is your tank maintenance regimen? What do you feed your fish? Do you quarantine your fish and how long? Did you buy all these fish all at once? Do you trust your source for fish? I asked these questions because I feel it necessary to study through your routine and correct wherever may have gone wrong leading to the demise of your fish.
Secondly on the treatment, how high did you adjust your temperature? How did you administer the salt? What salt did you use? How much salt did you dose? Did you dissolve it thoroughly? Did you add the salt slowly? To explain this, high temperature depletes the oxygen necessary for the fish to survive. Ich resides mostly in the gill tissues despite the fact they can appear on the epidermis of the fish as outbreak therefore gills are the weakest point of the fish so unless there is adequate supply of oxygen, the fish succumb eventually to the damage done by ich. Normally, ich does not appear unless your fish is weakened by stress due to the changing tank conditions or when you fail to quarantine your new fish to safeguard your current stocks.
As for salt, table salt or "aquarium" salt are the ones you must use, not marine salt, epsom salt and anything else. Table salt is a much cheaper option so go for this one. Marine salt has buffering properties which will adjust your water chemistry unnecessarily while epsom salt is not purely sodium chloride but magnesium sulfate so these are the wrong types of salt to use. Adding salt too fast will lead to osmotic shock on the part of the fish. How does this happen? To explain this one, salt adds electrolytes to the water. Fish have osmoregulatory system that enables them to handle the appropriate amount of electrolytes. Since we are talking about severums, severums happen to originate from soft acidic waters so the amount of electrolytes there is very low comparable to hard alkaline water. By adding the salt quickly, the electrolyte amount jumps quickly thus the osmoregulatory system is unable to handle the sudden increase of electrolytes causing the fish to become shocked and in some cases, die slowly from the severe stress caused by this reaction.
For future reference, administering salt takes patience. Get a cup of tank water and start with a tablespoon of salt in it. Keep stirring until the salt dissolves thoroughly. Then slowly pour the cup of salt into the tank. Repeat this process every 15 minutes until you've accomplished the maximum amount of salt required for the size of tank. The recommended dosage is a tablespoon of table salt per 5g so in your case, you will need 10-11 tablespoons. Do your water changes every 2-3 days and add the amount of salt per the water volume replaced.
In your current situation, leave the tank empty (but with water) for at least 48 hours as the ich will be unable to find any host and will eventually die from the lack of host. There is no dormancy period for this parasite so the lack of available hosts for at least 48 hours should be enough to guarantee you to add fish safely afterwards. When you add your fish, monitor your water parameters first. The lack of hosts will kill some beneficial bacteria in the process due to the lack of ammonia source needed by the beneficial bacteria to continue the nitrogen cycle process.
Lastly, get a 5g tank as your quarantine or hospital tank. Operate it with a heater, sponge filter and few decors for refuge. No need to add substrate in there for hygienic reasons. A quarantine tank is a must regardless of the circumstances unless you are prepared to lose any of your current stocks in which case this is a win-lose situation on your part where you end up wasting your time and money to treat the fish when you should have quarantined the possible disease carriers in the first place. Give quarantine time duration for four weeks. Again, it takes your patience to achieve it. It's up to you to decide whether you want to risk your old stocks to diseases by new arrivals or not.
Good luck.