My rhuemy has me take folic acid every day. i don't think once a week is enough. My nails do not break and my hair is not thinning. I know everyone is different but maybe discuss taking folic acid more often with your doctor.
I also take fish oil and using solar oil on the nails is great.
My blood work goes up and down a little every time it's drawn too but not a lot. I think it's just the way ouur bodies work we don't stay the same every minute,
Good luck