I use GH 3 part as well and I pretty much follow the feeding schedule. Once you see them get a nice healthy root system and they are about 6in high, I just bump up the nutes to full strength. Until then, they get half strength and when they are seedlings they get almost a quarter of that. What I use now for seedlings is clonex, its a clone and seedling nute that is really weak but it is designed for little plants and it wont burn them out. if you ever see the new foliage turning a color like yellow or getting hard and crispy, then you know they are too much. Dilute it with a little water and in a day or two they should be fine. Its all about knowing your strain and how your certain nutes work. I would stick with the 3 part for now and just get that under control. If you are having issues with the regular, why would you want to make it harder? I would just try out the 3 part for at least one more grow and then try some other stuff.