Leave the burned parts of the plant alone. They might not look pretty, but if you cut them off you expose the plant to insects and diseases. Just let them be.
Keep the ppms there and under 500 for the next week or 2. Let them recover. Keep your water level up and you should be fine. You can leave the leaf or pick it off, what ever.
Take that reflector blanket off from around the plant as that also baking it.Reflecting heat and light right back up on suck a little guy is killing it.Room temp 85 plant air temp 110 and it cant breath.Put a fan on it