Ich is not bacterial, it's a parasite. IT had to have been brought in, probably on the Rams. Once the rams brought it, the tiger barbs are known to be HIGHLY susceptible to it.
When you use the salt method, you should be doing daily water changes, replacing the salt. I think some of your problems have probably come from non-pristine water, as they fish were already dealing with the parasite and in general not feeling too healthy. You may lose some of the barbs, they're pretty weak when it comes to Ich. If you continue doing water changes and salt, you should be able to get rid of it, and hopefully most of your stock will come through.