African cichlid scratching?

Question
Hello! I had a 55 gallon tank with 8 african cichlids. (3 bumblebees, 2 electric yellow, 1 ice blue zebra, 1 kenyi, 1 unidentified purple one) Then 4 days ago, I added 3 more which I THINK are 1 demasoni, another kenyi and i have no idea what the other one is.(they told me they were all demons, but they dont look right)  Anyways, now my older fish are scratching on everything. It's very rapid, and continuous. Once they start, they will keep trying for a long time. I know somethings not right, but I don't think it's ich. I do not see any white spots on any of them. So what could it be? What do I do?   I don't wanna lose my fish, but I also know that if you give them medicine for something they don't have you can kill them and that would break my heart so any advice would be appreciated!


I just did a water test;
Ammonia=0
Nitrates=20  
Nitrites=0
PH=7.4
KH=240
GH=180
And it's 74 degrees in there.

Thank you very much for your time!

Answer
Heather,
It is very important when bringing home new fish to quarantine them in your hospital tank for a minimum of 2 weeks before adding them to the main tank. The hospital tank has to be cycled and running at all times. It sounds like they have parasites. That is why they are "flashing" or scratching. The best way to treat is by ingestion. They have fish food that is medicated. I have found a product at Walmart that seams to work great. Its called Tank Buddies. You will be looking for the ingredient praziquantel.  Just make sure to read the directions of any medication that you use. Remember, always quarantine any fish you bring home so that if they are sick, you don't want them to get everyone sick.