What's wrong with her?

The purpling is usually due to cool temps at night. She is also hungry for Potassium (K) and a bit of extra nitrogen wouldn't hurt either. Add a P/K booster to your ferts and maybe give two feeds with half grow and half bloom nutrients to top up her nitrogen availability. After that go back to straight bloom nutrients and continue with the P/K booster until about 3 weeks away from harvest, as she won't get any extra benefit from the extra P/K (phosphorous/potassium) once she gets close to maturity. Going by your picture, you still have another 4 weeks or so of flowering to go, maybe even 6. Start a flush (in reality, just stop giving fertilizers and give just plain water, it is not an exercise in drowning your plant!) once she has 95-98% brown pistils and harvest when she has 98-99.9% brown pistils, usually about 2 weeks later, and this will put you in the "10-30% amber trichomes" zone without having to look too hard at your buds. Once a plant has 100% brown pistils, THC breaks down rapidly into CBD and CBN, which are 2 non-psychoactive cannabinoids that don't get you high, but they do make you sleepy! Hope this helps, Organoman.

Ph and or a lockout. And looks like it’s a touch cold in the room—maybe at night? You are getting purple leaf tips. Flush and get back on the bloom nutes

Nitrogen is mobile and starts at the bottom. Looks like potassium or micro nutrients deficiency. Make sure your pH is correct for whatever your growing in. My guess is it's not balanced causing a lockout.

Hey guys, those buds are looking beautiful, but what I see is the tips of the leaves starting to burn, it could be over-fertilization. I recommend watering only with water at 256PPM and 6.3pH. How much water? ... Just enough for it to drain out the bottom. For the water that comes out from the bottom of the pot, you’ll measure the PPM, and if it’s between 700PPM and 1300PPM, it’s fine. If it’s higher, then you have too many minerals in the substrate and you should water only with water again at the next watering; otherwise, increase the dose of P and K. You’ll also measure the pH of the water that comes out from the bottom of the pot, and if it’s high, at the next watering you do it lower, and if it’s low, you water with one that’s higher. With that technique, you’ll know the PPM and pH values of your substrate.

It's using up the nitrogen in the foliage. You also need to up the P in the diet.