Rep-Cal is just calcium. I use herptivite as the main multivitamin...the t-rex leopard gecko dust when I want to add D-3...and rep-cal for calcium dishes (same brand as herptivite). I've not used reptivite, so I couldn't give you any advice on it.
I use Reptivite, Rep-Cal ultra fine calcium, and Rep-cal calcium with D3. I have had no problems so far. All of my leos are doing really well.
I use the Rep-Cal ultrafine (w/o D3) every feeding for my babies and breeding females and every other feeding for my other adults. I use a mixture of Reptivite and Rep-Cal w/ D3 once a week.