When fertilizing plants, it is always better a light dose in each watering than higher doses every 2-3 waterings.
Yo can add 2.5ml each watering since the first week of growth and untill the second week of flowering (when finishing the pre-flowering stage). If you make a transplant, you can raise the dosage to 3-4ml for the next watering.
Another option is following the feeding schedule (see pics of the product) and gradually raising the concentration as plants get bigger.
Hope it helped,