Yup, it's right in there at about 4 weeks!

I am using tap water - left out for a *really* long time so that the chlorine evaporates. I assume buying a 5-gallon jug of distilled water is a better way to go?

As for feeding - until I see a bit of improvement, I was planning on feeding every time I water, taking a step up every two waterings. Is that a good decision, or should I do a plain watering in between? The soil dries out in about 4 days, which is how frequently I water.