help help help help 3 weeks into flowering what happened?

i think i might have burnt my top or something i dont know what i did but one of my girls is looking sick and its around the flowering sections i dont know what to do?

its just the one plant i have another one just as big right beside it and i have like 6 clones but this is one big mother of a plant already super bushy 3 feet tall 3 feet wide hate to lose it this close to being done

to much nutes it looks like?

i am using bloom nutes mg and i watered it once with nothing then 2 days later i renuted like always and now this it was right up between the fluoro bulbs so i thought i had burnt it with the heat but its at spots not close to the lights i been back and forth i will water only the next 2 times see if it comes back from this its mostly just the leaves the pistils look fine still