Hey mate, that looks like a calcium deficiency.
Check this out and look at the calcium deficient leaf
https://www.google.com/search?q=cannabis+deficiency+chart&oq=cannabis+de&aqs=chrome.0.69i59j69i57j69i60l3.3562j1j4&client=ms-android-samsung&sourceid=chrome-mobile&ie=UTF-8#imgrc=lvLKyH0CKVkJYM
You need to get some cal mag for her. Be careful as the often contain nitrogen so make sure to reduce the nitrogen element of your feed sufficiently.
Hope this helps 🙂