I've had my six Green and Golden Bell frogs since around June. They were being kept in poor conditions and fed badly at the time that I rescued them. Since then, it seems they haven't grown at all. The largest is around 3cm long, while smallest is 2cm. I know this is abnormal, as being young frogs they should be growing quickly.

What's going on? How can I help them to grow? Is it possible their growth was stunted from poor husbandry?