If the tank is not well-established this can be part of the issue. Water chemistry is still stabilizing on new tanks, residual chemicals also need time to be flushed out with water changes, and the amount of bacteria, biofilms, and algae also has an impact. So it is not uncommon that new tanks, less than 3 months run into this.
TopPupTomball 
If the tank is not well-established this can be part of the issue. Water chemistry is still stabilizing on new tanks, residual chemicals also need time to be flushed out with water changes, and the amount of bacteria, biofilms, and algae also has an impact. So it is not uncommon that new tanks, less than 3 months run into this.