Frankly, I don't see how a plant can go that long without nutes of some kind. Are you sure it was hydro? Just water and rockwool or rapid rooter? Must be some tough weed.
Soil really is the easier medium to use, however, hydro when it's done right, can really produce fast full growth. DWC is pretty easy. Don't plan on plants lasting two weeks without at least low fert dose, like 500-600 ppm and raise that as time goes on. I've seen a variety of different max numbers being used at the peak of the grow, like anywhere from 1000ppm to 17-1800ppm. I'm not familiar with measuring as EC, so can't comment. It's basically the same but the numbers are vastly different. ppm measures parts per million, if you're not familiar, and EC measures electrical conductivity of fert salts in solution. Both methods work, but I suspect that ppm, or tds as it can be called, might be better as it creates a broad range of numbers that can be easier to work with and understand. At least for me it is. But do what you want to. Remember that plants needs micro nutes, nutes in small amounts, like zinc and sulphur, etc., so that's why I advocate Dynagro as it's a one part fert with pretty much all the nutes plants need, and in your case this fert is good because you can use it both hydro and soil. Hydro just requires more of it in water. Follow the directions on the back. If you read the ingredients and compare with other ferts, you see that you only need one bottle for veg and one for bloom if you want to buy that. It might be a good idea to do so. don't mix them, just one fert for each grow cycle. The problem with this fert is that it doens't have a long shelf life because it has calcium and phosphorus in the same bottle. These two have a chemical attraction for each other and will bind together, rending each one useless. Other companies seperate these two, but the order to have all the nutes you have to buy at least one more bottle. The advantage is longer shelf life. You might be able to get the veg version of Dynagro in a small 8 or 9 ounce bottle. I know these exist but most hydro shops don't carry the small bottles and you have to buy the 32 ounce bottle. It you have a fairly large grow, then it might be best to just get the big one. Of course you can buy whatever fert you'd like. This is just my suggestion. No indoor grower should ever use vermiculite because we shouldn't breathe the dust from it. It's like asbestos, gets in your lungs and won't come out. It isn't necessary either. A 2000 Environmental Protection Agency study found that some vermiculite gardening products contained asbestos. The EPA did the study after vermiculite produced by the Libby mine was found to contain asbestos.