Hi I set up my co2 in a rio 125 and im using a AE glass drop checker with hagen ph test and premixed 4dkh but when I dose co2 its refusing to turn green! it started off as deep blue now its going lighter blue but no green just clearer in colour! Ive never had a problem befor could it be the 4dkh solution is off it it 8 months old? also ive changed my substrate to colombo florabase so my ph is sitting lower in my tank at 6.8 at the moment! Any ideas?