How do I avoid this next time?

I'm not familiar with your nutes at all but from what I can gather, this is all you're feeding them and therefore the NPK level doesn't change - i.e., they don't have one product for veg, another for flower... What I'm seeing in the tips and spotting is an overdose of nitrogen... Since your plants are in flower, the level of nitrogen needs to be knocked back quite a bit... and I don't know how you would do that with only that one source of nutes. What you CAN do, since I'm guessing you want to grow organically, is add a layer of wood chips or mulch to your pots... this will soak up excess nitrogen so it doesn't get to your plants (or at least not as much will get to them!). Start out with a flush with ph'd water, add the wood chips/mulch and proceed as normal... should do the trick. Going forward, I'd do more research into different nutrients to determine what is going to work best for you. If you want to continue with the coconut powder, just be prepared to add the wood chips/mulch when they get into flower (not before! veg state needs the nitrogen!). Best of luck to you... autos are a different breed and I find them quite exciting! The one drawback to them is that since they are literally pre-programmed, you don't have the luxury of changing up their schedule and you only have a finite amount of time in which to work. But your plants look terrific and your problems seem solvable... Happy growing!

It could be ph, lockout, nutrient burn, etx. So hard to say as they all look alike.