leaves turning yellow,white HELP NEEDED

Hi i just started using coco coir i,m using vitalink coir grow & bloom cannazym,hygrozyme & B52 in veg as i havent reached the bloom room yet i,ve noticed on some plants mostly seedlings that my leaves are going yellow then white almost with slight brown dots blotches at the tips any help appreciated i usually use cellmax & hydroton but wanted to try the coco-coir out any help tips well appreciated like i say some look okay others definately don,t Respect Growers if needed i can upload pics for yous if needed any help with this is well appreciated most clones seem fine as i say the seeds were doing great up until transplant i upped the e.c from 0.8-0.9 to 1.0-1.2 ph has been between 5.2-6.0 max thanks GROWERS!!!!!!