Here are results of my water tests if that helps. Nitrate- 60 Nitrite- 0 Hrdness- 75 Alkalinity- 0 and pH- 6.8.
Also I just did a water change 2 days ago. And added some highgrow plants over a week ago. Other than that there has been no new additions to the tank or a change in anything.
I don't think the african knives have electrical sensories? Only gymnotiforms? I could be very wrong..
The nitrates are a little high, lower than 30-40 is preferrable..
Did you test for Ammonia?
I would add something to buffer your Alkalinity. With an Alkalinity reading of 0 and very little hardness, any slightest amount of acids (ammonia) could causing your pH to drop heavily. This can be extremely stressful on the fish, especially more sensative ones like knifefish. Every feeding could be causing a swing in pH.