I have a 36 x 16 inground pool. Over the last few years, we have had problems with the steps turning yellowish. Vitamin C take it right off, but it comes right back. We went on vacation, and I forgot to fill the chlorinator. It ran out, but when we returned, the steps were bright white. I added clorine to the chlorinator and put 3 bags of shock into the pool. By the end of the day, the steps began to turn yellow again. Could it be the type of chlorine or shock that we are using? We use a Sams Club brand Chlorine for “All Pools.” Active ingredient, Trichloro-s-triazinetrione = %99. Avaiable Chlorine = %90. Shock is same brand, %99 Sodium Dichloro-s-Triazinetrione Hydrate. My pool store said that is could be due to a metal plate in our electric heater that will cause that in older model heaters (ours is 13 YO). The added chlorine has put doubt to that theory, and made me think that it could be the type of chlorine/shock we use or pool chemistry. I am curious to hear an expert opinion.