Goldfish breathing heavily after water change?

So I did a little over a 50% water change about three day ago, just because I didn't get to clean the tank for a long time and there was poop everywhere; especially under the ornaments. So I took all the ornaments out including the thing that makes bubbles, and disposed of the filter cartridge because I didn't change it for over a year (bad- I know). I was hoping to buy a new filter cartridge the day I disposed of the old one, but my parents kept putting it off.. and I noticed how my goldfish have started to breath more heavily than normal and the water is not that clear(it's not murky or anything..just little thingies floating around). Is it because the filter hasn't been on for three days? I'm trying to get a new cartridge asap.