why are my discus breathing rapidly

[JJ1]

this is my first post to this forum as usually i can get my answers by just reading the posts but this one has got me puzzled , i did a thirty percent water change 4 days ago and rinsed my cannister filters out in the old water which i have done before with all my other different fish in other tanks with this same trickle filter (i dont know if i had made a mistake as i have been trying to bring down my ph for a while now and read in several books that peat, ro and just boiling the water before you put it in the tank can make it soft ), everything went fine and yesterday my wife told me they were acting strange by breathing rapidly and going to the top and breathing then swimming back round but all the while they still had rapid gill movement , i have looked in all my discus books but they do not display signs og gill flukes or any parasites i am puzzled as i tested the water and the ph was 6.5 which had lowered and the nitrites had risen slightley above zero i just hope the rinsing of the filter cannisters has not caused undue poor water , as a precaution as in the books we did a 25 to 30 percent water change and today they are still having rapid gill movement but are not shy and have eaten blood worm will test the water again later at the same time of evening but if any body could help with advice i would be most gratefull
thank you
JJ1 :roll:

[revkev]

Your fish may be short on dissolved oxygen in the water try adding an air stone to airate the water. check your filter spray bars they should be facing the back of the glass and pointing slightly up to disturbe the water surface.Keep a check on your nitrite as you may have cleaned your filters too well next time clean one wait a few weeks then clean the other.