Illness/Sickness: Nonstop Gill movement. Please help asap?

So my little dewy, he's been through a lot he's about over a year old now but quite recently I introduced him into a new tank which was cycled for about a month before putting him in and I got my water tested; everything was perfectly fine from what I was told, twice by the way. The issue was that the tank he was in at the time had Insanely high nitrates so I had to move him asap. So I put him in, everything's been fine but now it's a few weeks later, I Just did a water 30% change and used some weekly EasyBalance as I've done for my third time now. Since I did that water change he has Non-Stop been flicking his gills. I understand it can be normal be he hasn't stopped for an hour now flicking them every 1-3s. Everywhere I read says that's a sign of high illness or stress or discomfort and I have No idea what could have caused this. He hasn't moved and barley wants to. He sometimes flicks them twice or three times in a row without stopping. Please give any insight I'm really stressing.

Some say it's the tank being oxygen deficit but I have a filter producing quite some amount of bubbles and surface agitation as well as a bubbler on the opposite side of the tank. Also I currently don't have any means of testing of water, when I can I'll upload the results.

If your axolotl was lacking oxygen, he would go to the top of the tank and gulp air from the surface. If he's moving his gills constantly it could be your water conditions.

It can take 2-3 months to cycle a tank, longer if you water temperature is below 70°F. If you don't already have one you should get an API freshwater master tester kit, available at your pet store or Amazon. Then you can get an accurate water parameter results. Don't use the dip strip water testers, they're not very accurate.