nutrient problems

can a plant have a nutrient deficincey before the colderas fall off? mine are yellow but have not fell off. two of my leaves are curling up and yellowing and 3 more are just yellowing. i think its an magnesium def. from what i read but i didnt think it would happen until the colderas fell off. any help is appreciated.

 

yea colytendons were the fuck did i get coldera. yes its only three weeks old i might be under watering it. and i bought a cheap soil test kit and the ph is fine so its probably underwatered thanx man