I doubt the PSI form the cold supply is more than 80. Most homes are in the 35-70 PSI range.
What kind of TDS meter are you using?
Has it been calibrated lately? 1 good way to check is to test a bottle of "aquafina" bottled water. I have consistently tested around 12 TDS.
How often do you feed the tank?
Try not feeding for a week and see if the green film on the glass gets better.
You could also try using another source of topoff water from a LFS. I know Saltwater Fanta seas has some REALLY good water.
How long has the tank been setup? Size? Fish Load?
If you have any mechanical filtration(filter socks, filter floss), it needs to be cleaned 2 times a week usually.
What kind of skimmer, and how is it working? Is it producing green tea, or dark coffee?