if you are going to get into topping you have to do this at least a week before flowering there is so much to do and think about when it comes to creating life... have you looked into fox farms? you dont have to have it but i like it a lot also keep the timp down in the 70s exc..............
The pH level of your hydroponic nutrient solution or soil will determine how well your plants are able to absorb nutrients. If the pH level is out of the proper range, the growth rate of the plants will slow down or stop.
When growing hydroponic marijuana the pH of the nutrient solution should be between 5.5 and 6.8. In most cases optimal pH is about 5.8 to 6.3 but this may vary slightly depending on the particular marijuana strain and the growing conditions you provide........ Veg around 4 weeks just keep an eye...