will transplant help mg deficiency???

hi, im looking at what i believe to be a mg def, ive 4 young plants about 4 week from germination, in biobizz light mix, in second pot, 1 feed, just with bio grow and rhizotonic,ph good, couple of days later ive got leaves turning rusty gold, theyre about 5" high been looking great till now 5-7 nodes, after a bit of research ( and posting ) i reckon its mg deficiency, i was wondering if i was to transplant up to bio bizz all mix which is a hotter soil would that perhaps sort it out? i planed on stepping up anyway but wondered if i need to sort them out before i transplant or if that might help in itself???
anyone got any input / experience in mg cheers

flush the plant. treat with cal/mg.

hi thanks for that, so do it before i transplant then and give them another week to recover do you think?