How is seasonal affective disorder managed?

Hi doctor,

I am a 20-year-old male diagnosed with SAD. My Psychiatrist prescribed me Tablets Clonazepam 0.5 mg, Escitalopram 5 mg at night, and Modafinil 50 mg in the morning. He also recommended some tests (Vitamin D and B12, thyroid profile, LFT, KFT). I started taking the medicines before my test results came. The results were: Vitamin D : 14.0 ng/ml, and vitamin B12 : 204.0 ng/ml. This shows I have a vitamin deficiency, but still, the doctor recommended me to continue with Benzodiazepine and Escilatopram. I have taken them for three days. When I asked my doctor about vitamins, this is what he said: Yes, vitamin levels need to be corrected, but I thought of waiting for a week because there are more medicines on our list, and if you show symptomatic improvement in terms of mood, I thought we could reduce a few medicines or doses so that you can be more comfortable. My question is: Since there is already a vitamin deficiency, should that not be addressed before going for Benzodiazepines and SSRIs and potentially getting addicted? Symptoms: Lack of motivation, laziness, anxiety, disrupted sleep cycles, and occasional suicidal thoughts.