I appreciate the civil, intelligent interaction on this thread.
I agree with several of the posters here.
Yes, it is possible to keep a plant green through it's entire life cycle, however it requires some finesse.
Sometimes we jump to over-analyze potential problems and by over correcting, we cause more undue stress to the plant.
The yellow lower leaves are not normal, and it is likely because of overwatering and possible nitrogen def , but overall other than it's diminutive stature, the plant is relatively healthy.
I would add a little kelp to help the roots uptake nutes and let it ride.
I use my finger to determine dryness of soil medium as well.
I grow in Berger BM6, which is a peat/perlite blend like Sunshine.
It has virtually no nutes and I must feed early and often.
It is a lot like hydro in that regard.
I too, used to get some yellowing of leaves. It took some time and adjustments, but most my plants finish "clean and green" now.
I still get different strains that do it to me in flower sometimes.