What are the ammonia and nitrate levels?
If nitrates and ammonia are 0, the water changes are not giving the tank enough time to stabilize. Weekly 50% WC is too much right now. Maybe shoot for 1/3 of the tank 1-2x a month. Then once your tank is fully cycled, you can do water changes more often. Otherwise, the water changes will slow down the cycling process. In the meantime, just don't overfeed and add some sort of cycler.