Not saying pH is the cause but here's something off the internet:
Acidosis and Alkalosis can be brought on in a couple different ways. The first is exposure to pH values drastically outside the fishes natural range for any period of time. A slow rise or fall of pH over the long term has subtle symptoms that can be hard to pinpoint the cause of without a simple pH test to see if they are in their natural range. These symptoms include gasping due to the changes in the oxygen carrying capacity of the blood or from excess mucus production that can cover the gills. Excess mucus production and reddened skin areas. Weakened immunes systems leaving them exposed to other diseases such as bacterial, fungal or protozoan infections.
The second way it can be brought on is through a sudden change in pH even as little as 0.2. Changes in pH should be made slowly to allow the fish time to adapt to the new ranges and should never go outside the fishes natural pH range. Rapid changes in pH can lead to symptoms that include the fish being highly excitable, rapid swimming movements, shimmying, gasping and excessive jumping followed shortly by death.
Acidosis and Alkalosis can be brought on in a couple different ways. The first is exposure to pH values drastically outside the fishes natural range for any period of time. A slow rise or fall of pH over the long term has subtle symptoms that can be hard to pinpoint the cause of without a simple pH test to see if they are in their natural range. These symptoms include gasping due to the changes in the oxygen carrying capacity of the blood or from excess mucus production that can cover the gills. Excess mucus production and reddened skin areas. Weakened immunes systems leaving them exposed to other diseases such as bacterial, fungal or protozoan infections.
The second way it can be brought on is through a sudden change in pH even as little as 0.2. Changes in pH should be made slowly to allow the fish time to adapt to the new ranges and should never go outside the fishes natural pH range. Rapid changes in pH can lead to symptoms that include the fish being highly excitable, rapid swimming movements, shimmying, gasping and excessive jumping followed shortly by death.