Lost weight, but not me

Uno and Abby has lost about 400g each since I last weighed them about 6 weeks ago. Other than this, both are very much the same as before... playful, alert and energetic, poo/pee same as before. Their rib cages are also not jutting out, although I felt that the fat layer covering the ribs could be a little thicker the problem is I do not know what is their ideal weight hence can only rely on the "feel rib cage" method to determine if they are over- or under-weight...

In the meanwhile, I had increased their food amount. Will review again when they regained some weight...fingers crossed