Hi
@MrWeebles! Tips are not really burnt, the yellow/brown comes from the margins and spots appeared randomly : to me it looks like a deficiency. Your plant is big, she eats a lot! She needs more nutrients, especially Phosphorous - Potassium - Calcium - Magnesium. You can try to add some cal/mag and a give it a good meal by increasing the blooming/flowering fertilizer doses in your mix. Hope this helps, happy growing!