Hard Water, and that yellowing after your buffers run out

[LOC NAR on probation]

It sounds like the water like you say. You need a filter or an R/O filter , it's the only thing that will help. Adding a buffer or anything will not do any good. You have to get the crap out of your water. Look at spending about 150 bucks for a filter. Check fleabay I saw some on there not to bad a price. You will not regret it.