Bro, this photo is taken from a cheapo 150W 6500K bulb. The hammer has been under this bulb for a year at least and is able to maintan the luminous colour. Only recently, I added in a blue tube (which is not actinic strickly speaking).
From my pass experience with hammer ( 6-7 pcs at least), i notice that they will start to brown out then slowly withered away. I think it has to do with yr water parameter, but then, its just my guess nia. Have u been testing yr water w salifert? I only trust Salifert so far as my pass experience w other test kit is they are not accurate.