Andi ~
To me what you have described represents oversupplementing. I dust crickets for hatchling geckos and juveniles at the same frequency as I do for adults. So far I have not had any problem doing so.
Moreover, Rep-Cal's calcium with D3 contains the highest level of any D3 calcium supplement I know. :-( Check out post #24 following my Leo Caresheet for comparisons of some major brands.
-------------------------------------------------------------------------------------------------------
On the 10 June 2013 I visited my exotics veterinarian with my leo and another gecko. The vet recommended Zoo Med's Reptivite with vitamin D3/A acetate multivitamin. He stated that only "a little tiny pinch of the multivitamin with D3" should be used 1x per week. He suggested formally gutloading the insects with T-Rex Calcium Plus Food for Crickets. He seemed satisfied that I feed Albers' All Purpose Poultry Feed to my crickets and to my dubia.
Continued advice is to feed the crickets a nutritious diet 24/7. Then 48 hours prior to feeding the crickets off to the geckos, feed the crickets only T-REX Calcium Plus Food for Crickets (the only proven gutload formulation as of the 18 July 2013). When using the T-REX Calcium Plus Food for Crickets only provide the crickets with water (damp paper towel), but no fruits or vegetables or they will consume those preferentially over the calcium-enriched diet.
Be sure to check the calcium-to-phosphorus ratio of any food feed to the crickets or worms. Carrots, for instance, are not good because carrots contain about a 1:2.3 ratio (???) of calcium to phosphorus depending upon the charts.
***Current directions (16 May 2013) on Zoo Med's Reptivite with/without D3/A acetate
"Directions for Insectivores: Place crickets in a plastic bag with a small amount of Reptivite w/d3 and shake to "dust" crickets with the powder. Feed approximately 12 dusted crickets per week for every 2.5 ounces (71 grams) of body weight."
So if your leo weighs 24 grams, the recommendation would be only 4 lightly dusted crickets per week with Reptivite with D3. Baby leopard geckos weigh much less, so be sure to adjust the dosage accordingly!
Do not exceed the recommended amount of Reptivite per body weight. One real problem in recommending exactly what to do is the size of the crickets fed.
Suggest using Zoo Med's supplements like this
1. Monday - Repti-Calcium with D3 on all crickets
2. Thursday - Repti-Calcium with D3 on all crickets
3. Reptivite with D3/A acetate adjusted for your leo's weight: Best to spread out the Reptivite with D3 dusted crickets over the course of a week.
Reptivite contains vitamin A acetate in contrast to the beta-carotene provided in Rep Cal's Herptivite. There has been research with chameleons which suggests they do not utilize vitamin A in the form of beta carotene.
Beyond the formal gutloading right prior to feeding off and dusting, feed your feeders a nutritious diet 24/7. Feeding off crickets whose entire body is healthy (and not only their guts) is very important!