Hello there , For a 7 month old, Prefer to visit a pediatrician rather than dermatologist.
Regarding white patches, they are common in infants.
1. It can be pityriasis alba and needs no treatment.
2. Fungal infection - needs antifungal cream application
3.
Vitamin d deficiency - just needs maintenance 400iu daily dose. Not such high doses of vitamin d rather now.
Do Consult online and get prescribed properly with shared photos for proper treatment