Help coolant almost dry

[prism]

Just when I was getting over the discovery that the engine oil of my car was almost dry, this morning I decide to look at the engine coolant compartment and the red stick is well below its minimum level. Once again I did not get any OBD warning indicators light up so it was just pure chance that I had a look. Since the stealer is closed over the weekend, BMW assistance told me add some water which I did! My car is a year old, is this normal? Should I have had a warning sign light up? Was adding water the right thing to do (doesnt it dilute additives in the coolant?). Really appreciate your help on this!!!

P.S. I just realized that I needed to add distilled water. The BMW assistance guy told me tap water would be fine, am I damaging something here? Man, this BMW experience has been nothing but stress, what a bummer!