Hi Gautam and welcome to Tropical Fish Keeping forum.
I'm afraid you have some issues with your setup. First, Goldfish
need a lot of room, and 17 Goldfish
in a 33g aquarium is way overstocked. If you read the Profile on this fish [click on the shaded name in posts to go to that fish's profile, or click on Tropical Fish Profiles in the blue bar and find the species] you will note they recommend 10 gallons of water for each fish.
Second, water changes once a month with so many fish in the tank is no where near adequate. A 50% water change every week is basic, but that works when the fish load is reasonable to balance. In your siutation, for the health of the fish, it should be changed more often than that if they are going to remain in the 33g. I would stongly recommend you upgrade to a very large tank or consider re-homing several of the Goldfish
to create a more balanced bioload. Goldfish
produce a lot of waste and this affects the water quality, which I would guess is the source of your cloudy water.