Urgent help needed pls asap

Hey guys I'm having some issues here and I'm hoping some of you can help. My leaves are getting brown spotting turning yellow and dying my set up is a Dwc drip feed under 600w hps. I'm using general flora trio (soft water) nutes at quarter strength the room temp varies between 70-83f depending on time of day I have them on an 18/6 timer oh I'm also using hydro guard for root protection. Any help would be gratefully received thanks guys (pics to follow)

This is just a cal mag deficiency. Give it a dose maybe a bit of nitrogen not very much she will be fine.

Thanks a lot mate I done a bit of research thought that may be it but was thrown off by the new growth being healthy. Much appreciated

1tsp per gallon cal mag is plenty.