After I typed the reply I went back to our log books. Evan was only 9 pounds at 2 months. We were basically in the hopsital for the first two months of his life - a few other thoughts:

We give Evan 1 1/4 strength formula. In other words for 16 oz of water, we use 10 scoops of formula. This was also our pediatrician's idea.

Also, Evan takes an iron supplement. When we left the hospital, Evan was highly anemic to the point of needing a big transfusion. The iron supplement has prevented any new anemia.

Icthyosis eats up a lot of calories, thus the extra formula powder and skin uses up a lot of iron to grow, thus the iron supplement. Your precious babe is not failing to thrive - her skin is the cause!

I hope this is helpful.
Best wishes and kind thoughts.