Your muscle aches and fatigue fit both deficiencies well, and in an active badminton player low D3 also raises the risk of tendon and stress injuries.
Vitamin D is corrected with a weekly high-dose sachet for 8 weeks followed by a daily maintenance dose, and
B12 either by injections for a few weeks or a high oral dose daily if the level is only mildly low. Do not keep taking loading doses indefinitely - recheck both levels after 3 months and then decide maintenance. At 50 with low B12 I would also check
TSH,
HbA1c,
creatinine and, if B12 is very low, look for a cause like metformin use, vegetarian diet or gastric absorption issues. Share your actual values with me on a Practo consult and I will give you the exact dose schedule instead of a generic multivitamin.