water quality problems can be ammonia, nitrite, nitrate or PH.
Any ammonia or nitrite will cause stress and if the PH is above 7.0 then any ammonia present becomes extremely toxic.
Nitrate levels above 50ppm can cause stress.
If the PH is different compared to where the fish came from that will cause stress. Also if the PH is extremely acid (below 6.5) or alkaline (above 8.0) then that can cause stress.
sorry about the late reply, I only just got the email.