I would top off with regular tap water. Yes, the plants are going to take up a lot of minerals and stuff. But most of it is going to be replenished by fish food, and plant fertilizer. Tap water makes up for any micronutrients that end up missing.
Of course, the best way is to just top off with tap, and then do a water change once a week. This helps to reset a lot of changed values.
So many fish/plants/inverts to keep, not enough aquaria.