Sorry to hear that you are struggling with your monti and lepto. The tank looks like it may be fairly young? Is that the case? Both of those frags look like they haven't been with you very long either. How long have you had them?
What are all your parameters including, nitrate, phosphate (yes I know you already provided this one), calcium, alkalinity, magnesium, lighting, and flow. All of this info can help everyone help you determine what might be going on with your corals
I know it is frustrating to lose things in the tank. Don't give up though as it is a process to learn what all these animals need.