Switch feeding schedule?

More recent studies show a lot of the beliefs about this are most likely false. It all depends on how much you fed over time so far... since people do such drastically different things at times, it can mean drastically different needs at this point. the plant uses roughly the same amount of p and k during vege and flower. You may need a bit less N in flower, but nothing like a lot of rhetoric recommends.. for example, zero or near zero is just stupid. There is reputable, repeatable quantitative data that shows this is false. It responds well to N in flower. By taper off i mean i go from 120-130ppm to 110 or so. A 10-15% drop? give or take. I taper off N down to 110ppm after a couple weeks of bloom, but i've had a bit of darkness creep in last couple weeks of flower on 1-2 plants out of 10. I will attempt a slightly different path next time and hopefully avoid the rare plant showing this issue. This is about what you do over 2-3 months and not last night or the last week. It's simple, but not that simple. I probably feed a bit too much N in vege, but it takes a long time to be an issue later on. read and react.. always do what the plant says... take and course corrections and adjust feeding habits next time to avoid it. If you do that, you'll have a formula that works for 99% of plants with zero issues seed to harvest... a very reasonable goal for anyone. People make WAY too much out of growing healthy plants. The plant does all the work.

For an example of what happens when you switch too early, scroll down a few questions and look at the plant in the panel "can I still finish?" posted by adkguerilla.

Too early to switch, pre-flowers is not flowering. "Pre-flower" as the name suggest, is just an indication that flowering is about to start, it is not actual flowering yet. Flowering will start properly in 2-3 weeks and this is when to start with flowering nutrients. Plants still need adequate nitrogen at this stage to help with the "stretch". I generally wait until there are small "budlets" starting to form before switching. In fact, at this stage that you are at, I keep going with grow nutes for the next two weeks, then go to half grow and half bloom for the following two weeks, then finally change to just bloom nutrients. I have been doing this for thirty years and it works for me. This method seems to give the plants the best start to flowering and helps prevent the plants from starving themselves towards the end of flowering and ending up a sickly yellow colour when mature.

This will vary greatly on your bloom fertilizer you will be using. More often times than not, bloom fertilizers do not have an adequate amount of nitrogen to get the optimum level of stretching. (Also sometimes you do not want much stretch if you are limited on space). If you have the environment and would like bigger plants then stick with the grow fertilizer for the first two weeks of bloom. Hope this helps.

I like to keep with Veg based nutrients till end of stretch as the plants are using up lots of N in that growing period. Then once stretch is done and over with move over to bloom based nutrients if your feeding guide uses em. An all purpose feed can work from seed to harvest its just not as specialized as other formulas and it may not get as many blooms on them. Good Luck!

The product I use (General Hydroponics Flora Trio) gives a schedule for the transition but absent that I'd probably run veg nutes those first couple weeks. Nitrogen demands are still pretty high during the stretch.