My tank is all mbuna cichlids. I have two orange zebras that are kind of nasty, but they don't really bother the yellow ones. I noticed yesterday that this particular fish wasn't coming up to eat. Today I noticed him laying in the plant. He died a few minutes after my post. The water tested fine, all other fish alive, hungry and active. I have three other yellow ones, they are shy, but seem fine.
Thank you for all of your help, once again.