cracked leaves

hı ıma newbee closet grower for the fırst tıme and desperate for some advıce ım growıng cherry x grapefruıt 40/60 satıva-ındıca and ım usıng an all natural soıl (plus prlıtes) under a 400watt mh bulb dıstanced at 50cm above the plants around 40/50% humıdıty and around 25 to 22celsıus my...