There are a couple of potential problems that I can see,
The salt you have added is fine for the majority of the cichlids but it is not recommended for use in situations where you have plecs in the tank. The reason being is that it aggravates their flesh. Also, the addition of salt is only really necessary if the fish have been exposed to stressful condition such as ich, external or internal bacteria or if you are treating with medication that reduces the dissolved oxygen content of the water. Other wise I would stop adding it.
The kenta pete that you have added is full of tannins and decomposed organic material, this will lower your pH making it suitable for some of your fish but not all of them. You are going to have to decide if you want rift lake cichlids or central/south american cichlids. By your species list, I would suggest that you return the ruby red peacock as they prefer a higher pH. Although, yours is 7.1 this is really the lowest they should be kept in.
I would also suggest that you do not buy anymore fish until, you decide on what variety of cichlid you would like to keep and wait a few more weeks to see if any more moralities in the current stock occur. Introduced fish will be far more susceptible to adverse tanks conditions if there are any, the LFS will always have more fish so there is no rush to buy.
Regards
Denis