If the root zone is hovering around 65-70f, go check with a cooking therm. If cold, you're mostly likely locking out mag which is a catalyst for chlorophyll production etc. In this stage flowering doesn't need much nitrogen hence the low amounts in formulas. This leads to others that trigger colour deficiencies. Potassium can be depleted within a plant in 3-5 days so if slowed growth is what your noticing, that's it! Also for me it accompanies crispy brown leaves...
Used in the biggest amounts for flower is in P for bud sites, K for maintenance/health, and cal/mag next. Now the plant will draw semi mobile nutrients from leaves to continue growing so those are the beginner suspects. Start with a clean flush, an balanced nutrients.(if not done yet) See what happens... Eliminate one by one till desired effect is achieved. Now the PPM is low for me, yes. But these are your plants, you know better than anyone just like a persons own body... Arm yourself with knowledge and learn from those experiences!
There is a reason multiple additives/amendments are on the market, yes some for bullshit, but you get to pick and choose. If you find nitrogen deficiency in some strains you can supplement with a product to increase this strains production while using a regular balanced 2 part for the rest that don't like it. It's all about experience! Get you some!
