Littles burn tips and some cracks are visible in the pictures on some older leaves.
Are they nut burns? It is a fully living organic grow, no added nutrients what so ever only bubbled water.
Yes it is a mild nutrient burn. The dark green leaves show that it is a little heavy on nitrogen. Nothing to worry about. The plant looks healthy and happy. Just keep doing what you are doing and it looks like you will get some nice buds off her. Good luck finishing her up!