Lower leaves are yellowing (young plants)

Hello, I'm pretty new at this, I'm growing sour diesel in coco. I've been using the recipe for success nutes, and watering roughly every 3 days when the soil is completely dry. Lately I've noticed that my lower leaves are yellowing and the upper leaves look great what can this possibly mean? I always keep the ph in the 5.8- 6.5 range.

Did you prep the coco before using? Foliar spray a ca solution of 2 % and the next day with a 2% mg solution. Ramp up the ca and mg levels in watering.

I did not prep the soil, but I do feed small amounts of calmag for every watering. Should I maybe give it a full dose of calmag when It gets plain water?

Do the foliar first then youll be able to pinpoint it.

Do I spray directly on the leaves? Thanks

That was a stupid question as I just checked what foliar spray was lol. Should I spray a calmag solution and see what happens?

Yes