Summer Project

Just going to call the 8th of May Day 0, so that would make this the start of week 7? Plants started flowering 2 weeks ago anyway. So far I've been watering the plants every two days or so whenever the plant looks like it needs it. Ive been using a 500ml bottle with a few holes on the top so each plant is getting 500ml For nutrients I've been using the Advanced Nutrients starter kit and mixing the nutrients in order according to the legend. I mix my nutrients in a 2L bottle, last week I fed the plants Sensi Bloom A&B 4ml, Voodoo Juice 3ml, Big bud 3ml and Bud Candy 3ml. Total of 13ml of nutrients in the 2L container. This burnt the plants :( Would appreciate any advice using these nutrients. Each plant gets 500ml from the 2L bottle and whichever plant is responding best gets the leftovers. New additions to the tent, a 20w oscillating clip fan and a Co2 bag which has been hanging for about 3 weeks now and plants seem to have boosted since its arrival. Tent settings for the passed two weeks have been 70-80°F with and Rh @ 50-55% - Gorilla Cookies is doing the best in my opinion its small but strong was topped around week 3/4 and trained from week 5 - Gorilla Zkittlez is the biggest but very thin and red stalks could be a nutrient issue, definitely has more bud sites but seem to be very small and wispy topped around week 2/3 and trained from week 4/5 - Gorilla Strawberries is doing the worst loads of crispy yellow leaves seems and seems a bit lifeless, the stalks are firm and green but the leaves are sagging. It definitely needs some nutrient to help bring it back to life a bit, I've been only feeding this one water which has been brought down to a pH between 6.2-7 Any advice would be greatly appreciated :)