Is it just the 4 shubies in the 44 gallon or is the comet in there as well?
Either way, you are a bit overstocked IMHO. 15-20 gallons per fish is generally recommended as a minimum for goldfish since they do have the potential to grow so large and have such a heavy bioload.
How often do you change the water and how much are you changing at a time?
In addition to being a bit overstocked, my guess is that you may not be feeding enough. Feeding .5-1% of body weight in dry food a day is a good estimate for young goldfish. For wet foods like the repashy 1-2% of body weight is more ideal since the nutrient content isn't as dense as with a pellet food. You can use a digital kitchen scale if you have one to weigh your fish and get an idea of what you should be feeding (place your fish in a bowl of water on the scale). Also, more frequent smaller meals are better than one or two larger meals. How often you can feed will certainly depend on your schedule, but you may want to try breaking their meals up into 3-5 a day. My fish typically get fed 1% of their body weight spread out across 5 meals a day depending on my schedule. I have a general sense of how much they need to be fed and it is easy for my to just throw in a pinch of pellets when I walk by the tank every few hours. I have also used auto feeders in the past to feed small meals throughout the day.
Some fish are naturally smaller than others, just as some people are shorter than others. Genetics play a role in growth as do feeding and environment. Fish exposed to poor conditions when they are young may not grow as fast (poor water quality, stress due to overcrowding, and lack of adequate food due to overcrowding all play a role in this), however most 'stunted' fish are able to continue growing once provided an appropriate environment and adequate food.
So, my advice would be to consider upgrading your tank if you are able and also to try increasing the amount you are feeding
If you don't want to go through the hassle of weighing them, you can simply try increasing the amount you are feeding, but watch your parameters closely since increased feeding equals increased bioload.