Good time to start adding flower nutes?

No, this is a common mistake among new growers, switching to bloom nutrients too early. Cannabis still needs adequate nitrogen during the first stages of flowering, it is not until mid to late flowering that nitrogen requirements really drop off. At this stage, your plant is only showing that flowering is about to commence, it is in the strictest terms, not flowering yet, just thinking about it. What I have been doing for 25+ years and it seems to produce the biggest blooms on plants that do not exhaust themselves by maturity, is to continue with grow nurients until there are small tufts of pistils/budlets formed. After this, I switch to half grow and half bloom for the next 2-3 weeks, depending on how fast flowering is progressing, then and only then, change to straight bloom nutrients through until maturity. As I said earlier, I have been doing this for 25+ years and refined this technique over the previous/earlier 10+ years, before settling on this technique, and can honestly say that it works really well and would not recommend it to anyone if I did not think it was 100% effective. Remember too, the best routine is plain water/plain water/feed/plain water/plain water/feed, so that the plant is being fed every 10-12 days when growing in soil. This is perfectly adequate and will help prevent burning from over feeding. Watering until run off (water coming out of the bottom of the pot) is also vital to stop nutrient salts from building up in the soil, as is waiting until the top inch or two are dry before watering again. Watering too often and not enough are common mistakes, something that must be learned through experience, but is entirely avoidable if given good guidance from older and more experienced growers. 😉 Eventually you will "just know" when to water, how much to water and the same with feeding. It is also easier and better to under feed slightly as it is to feed too much or too often, as it is very easy to rescue a slightly under fed plant, but very difficult to rescue a badly burnt over fed plant! If unsure as to when to feed again, err on the side of caution and wait, or just give half strength feeds, which most often is more than enough, especially if growing autos, they need less feeding than photoperiod plants. I also prefer to feed with lower doses in general, if for example a nutrient says give full strength every 14 days, I prefer to give half strength every 10 days instead. I have found cannabis prefers gentle, steady feeding often, rather than high concentration "nutrient spikes" less frequently. Hope this helps, Organoman.