Phrag leaf tips turning brown

[Connie Star]

I have a Phrag cariaciaum x sargenteanum that I bought in bloom. It flowered sequentially for me for 3 months. The leaf tips have been turning brown for about 2 months now. I water it, usually 2x per week with distilled H2O, keep it in a saucer filled 1" with water and fertilize "weakly weekly". I do mix the fertilizer with my hard water. The newer growth on the plant looks very healthy.
I also have a Phrag klotcheanum which I brought to flower myself . It is right next to the other Phrag and gets the same treatment. It's leaves got much worse before I trimmed them away, and the remaining plant looks good.
So my question is, is this normal or am I doing something wrong. I love phrags but has my initial good luck in getting one to bloom given me false confidence?