Apparently the 35% is "food grade." Whatever, I wouldn't drink my nutes either and I feed them to the plant. I doubt there's anything terrible added to the 3% besides distilled water. After all, it goes on open cuts!
The only difference between food grade and regular is the regular has a high concentration of metals and it wouldn't be good for us to drink. But then again, I probably wouldn't be trying to blow my stomach up drinking food grade peroxide either.