Dark Leaf Tips - help

Plant seems otherwise healthy but I noticed the leaf tips turning black/purple.

Is this normal, minor nute burn or am I killing the plant? Lol

Looks good, reduce nutes in the final 2 weeks.

Nothing wrong -when a plant is ready for harvest many times it changes color,ect - How long in flower? As "Buds" mentioned it loks like you should stop nutrients and flush then harvest your work

It's only about 25 days into 12/12

My last feeding was plain water and Azamax (keep gnats under control) and I'm planning on doing the same today. I'll keep the nutes out for the next week or so (would it still be ok to add silica?)

The "silca" will strenghten your plant (no harm ) you are in middle flower stage and should be feeding a higher K the P - till week 5 then higher P than K as for flower boosters = what nutrients are you useing ?

I've switched over from FF grow big to tiger bloom, Mad Farmer silica boost, GH CalMag+, gave them a small amt of Epsom salts earlier in veg., and I've given them them molasses once so far.

Also, Ph up/down as needed.

(I'm in soil)