Help with GH Nute solution

Ok so I think I read somewhere not to go with General Hydroponics nutrient calculator, without an EC meter how do I know what to mix in my DC, my last change started to burn them so Im in flush right now. One of my tanks is 6 gallons, the other is 9 gallons. I have been using Sensi Grow, but my Hydro guy was out and recommended GH. But I burned them immediately. Ugggg

get a meter. i know it sucks whenever someone tells you to buy more stuff, but hey, harvest time comes and it will be worth it.
i use GH. you probably read not to use it from other people, thats probably because they see better results using other nutes with different types of strains. im sure there are lots of other companies out there that makes better nutes than GH, but to me, i stick with it because to me it is consistent, pretty affordable if you ask me, and very basic and easy to use.
iv also tried advance nutrients with good success on kush strains, but i will be sticking with GH on strains that arent so hard to maintain.