"feeding" straight distilled water for more than one to two days is a recipe for unhappy plants. Plants dislike large changes, so if you go from pH'd tap water or light feeding to only distilled water without any buffers the plant doesn't like it. This can contribute to toxicity issues or deficiencies.
The short version is that your plant's soil is a complex bunch of chemicals. When you feed tap water or pH'd distilled water with some added ferts like CalMag and Silica, you have what's called a buffered solution. This means that it takes more of an acidic or basic chemical to cause the pH of your feed water to raise or lower.
Why is this important? Because decent soil is generally fairly acidic with an ideal pH in the area of 5.3 -5.7; the sweet spot is usually considered to be 5.5
When you feed pH'd water (or even plain city tap water) it's usually close to neutral - typically 6.7-7.2. When it interacts with your soil this brings the root zone to around 5.8 to 6.3 if you've got your stuff all in order. This is absolutely vital for your plant, as cannabis can't absorb nearly as much nitrogen/phosphorus/potassium at levels below 5.5 or above 6.5
How does this affect using distilled?
If your water has no buffering capacity (distilled, or reverse osmosis) it'll rapidly change to the same pH as the soil. This interferes with both nutrient and water uptake and makes your plant rather unhappy.
If you have the ability to pH your water, take it to 6.5-6.8 and feed just that for a few days before adding any more fertilizer. If you do want to add ferts after this, stick to some of the well known brands Bloom line, like Fox Farm. Make sure whatever ferts you use isn't "Hydroponic" nutrients, they tend to be formulated differently and aren't easy to work with for soil. Start with a quarter dose and work your way up.
And remember: You got this girl all the way into week 5 of flower. Even the best growers here have hiccups in their grows. Don't panic. Make changes gradually and you'll be fine.
