Instant Ocean is a fine aquaium salt, as I believe the poster above just ment that you are using an approved salt for aquariums.....
And you have not done anything wrong to this point as far as salt is concerned.
Also, epsom salt I know is used for Magnesium, but have never heard of it used for potassium???
Hey, we have all made mitakes with our tanks, nothing to worry about, just learn from. I just want you to know that no 2 reefers will do things the same........ we all have learned something diffrent and adapted our own styles. I ask a question to many people to get diffrent responses, then do it my way..... through a combination of all the answers I get that I like. You have done alot to be in this hobby for 2 years and not be bunt out on it yet. NONE of us know it all, but we are all here to share our trials and errors with eachother to make us better, together! (my 2 cents, and I'm off my soap box.... next.....lol)