There are a couple ways to balance any "propellor". I used to dynamically balance aircraft propellors to nearly perfect balance with computerized equipment. It sounds like you have pretty limited resources so let's go with the easier options.
The first is to remove the hub and blades as a unit, mount them on a spindle/shaft, set both ends of that spindle on a flat surface (so the blades are vertical and can rotate), and see which blade rotates to the bottom. You then add/subtract weight from the lightest/heaviest blade). I'm not sure this is possible with any of the wind turbines (not sure how the hub mounts to the unit).
The second is to remove each of the blades and then match all of them so they weigh exactly the same amount AND the weight is distributed evenly. That involves weighing the hub end of each blade and adjusting til they all match and also weighing the tip end and adjusting til they all match (like connecting rods on an engine).
There are some other factors (like blade tracking and even pitch) but I would start with matching the weight of all the blades.
The "type" of weight you use isn't terribly important. "Heavy" tape, lead tape, lead stick on weights, spray paint, etc... all work. Once you get it balanced note where the added weight is and how much and then afix the weight permanently. A taped on penny is great for the initial effort but won't last very long in normal operation.
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