The symptoms as mentioned by you suggest that the skin of your son might be allergic to the constituents of Lactogen 2.
In such situation, it will be better to discontinue Lactogen 2 & look for other baby food
But best thing would be to give him natural weaning foods like soft porridge, mashed potato,etc in addition to semi solid food like Rava and Ragi which you are already feeding him...cow's milk can also be included in the diet plan
Also keep an watch if he is allergic to any other kind of food product.
Wishing your son a good health.
Thanks & take care.