Looks like nutrient burn on the tips and possibly a potassium deficiency but it's hard to tell for sure without more detail. Is it possible you have a ph issue in your growing medium and are getting early signs of nutrient lock out? I once had nutrient lock out from having wrong ph in soil and it started a lot like that. Maybe try flushing your growing medium to get rid of any salt build up, test the ph and correct if off. I'd definitely try this before giving her more nutrients, if you have lock out the nutes won't be used and could actually do more harm than good adding more. Hopefully a 420 expert grower can confirm the problem for sure, good luck sorting it out.