Yellow leaves tips

It's very possible it could be nutrient burn, relax on the nute's for a feeding or two and keep a close eye on her to monitor for any improvements.

new growth is a bit thin and slightly pale? i'd wager this is too much P... a common misguided instruction from many fertilizer brands and forum posts. hard to be sure with so little info of how it was fed over time. more than one thing can cause burnt tips. soil adds more difficult to diagnosing, too. many unknowns as far as what is in the soil along with complications of needing bacteria to break certain molecules down etc etc... understanding what you've done over the last several weeks goes a long way here. make your best guess. you can look at a leaf symptom chart as well as the next person, but you have more info available as to you exact behaviour over last several weeks. this sort of stuff doesn't happen overnight, and if it does it's a major imbalance to move so quickly, otherwise weeks maybe a month or more needs to be considered as far as recent behaviour.