Looks like calcium deficiency bro. Look in your mars hydro instructions it will say to use Xtra calmag. Something with quantum board LEDs and calmag deficiency. Advanced nutrients sensi calmag is awesome. Has some nitrogen and iron in it. And Advanced nutrients rhino skin or any brand with silica. Helps strengthen the stems the leaf cells and its a trichome producer. Gets em frosty. But I'd get the calmag for sure and you will thank me bro 🤜🤛