Never cut your plants unless you are cloning. If you cut it will divert nutrients to repair the damaged part of the plant and start new growth. I dont know about the spots on the leaf itself (doesnt look too bad to me), but as far as the tips go that is nutrient burn. Stop giving them whatever ferts or nutes you are using and stick with water when they need it. The spots on the leaves might be from burn (really not sure, but my instincts make me want to say nutrient burn there also)? What are your temps? No matter what just start using water...if the yellowing continues flush your soil.