Kate,
You can lower your ph safely by using Sulfur sold for Analyzes and Holleys. I think it's called 'Holley Tone'. Mix with water and just water it. I have used this for my Sansevierias, then all my African succulents like Huernias and Stapelias. I don't think you can lower the ph down to 4.5 but close. To go much lower you may have to go a purer sulfuric acid or battery water. It gets very dangerous at that level for both you and your plants. I never heard of going down that low. Usually 6 - 7 is good enough.
Stush
