Adding something with a higher Iron content for there feed might be beneficial, Sprouts, cabbage and kale fill this bill.
Crickets are a little bit thick and will eat the easiest thing they can eat. In your case this would probably mean they ate more fruit than Veg.
We feed ours only cabbage/kale, carrots and potato. To further add to this the cabbage and kale we feed is home grown when in season. Cabbages are superb plants, they will over winter a frost, and you can take the leaves off the outside of the plant for animal feed well before there ready to harvest with no affect on the plant.
The reason for home growing is simple. We can monitor what chemicals are on that mainstay food. Meaning the crickets have less chemicals in them when they get to the animals. It's a sad fact that most veg/fruit will have been sprayed dusted with some very potent fungicides, and Insecticides at some point. And in a lot of cases this will appear in the animals that feed on these products in larger quantities as these chemicals are designed to stay in an animals system and overload it.
An alternative may be to harvest dandelions from the local wastelands. They will be clean of pest killers, just make sure there have been no weed killing operations going on! Also make sure that your pet is not going to have an problems with them as they do have minor toxins in the plant.
As for lettuce we were told to avoid it. It has very high water to nutrient content. To the point where it's not a lot of use to most animals. All it does is fill your crickets up and make them hollow. (think of a panda eating bamboo they need to eat masses every day because of it's poor nutrient content, so although they eat a lot they don't get what they need from it).
Carrot is very important because of the keratin content. It's a protein that helps you make strong finger nails, or in the case with a lot of animals scales, horns, or fur. It also helps the insect develop the correct thickness of chitin.
Hope this has been of help![]()