Toddler not eating properly

Golden Sunrise...

My son aged 21 months is not eating properly from more than a month now while before he used to eat his breakfast, lunch, snacks n dinner in a healthy and whole meal way.... n now he rarely eats anything of his favorites which he used to eat before.. n less quantity..

his loss of appetite is worrying us much.. however he is active and plays well.. so don't feel the necessity of seeing a doctor.. as they said us to reach them when child denies food including milk and is less active...

Kindly suggest me what I can do..

I am right now giving him below energies for more than 2 weeks..

GS+BCS+SO7R+ PHS+ WGS

Thanks in advance