There are many options for iron, as Raymond mentioned, tetra pride and leaf zone or even flourish iron are good choices. CSM+B works as well, ferrous gluconate, DTPA chelated iron, etc... should all work too. Adding iron should help the plants to recover very quickly, unlike most of the other deficiencies leaves that are currently affected with iron deficiency tend to recover somewhat within about 3-5 days.
The good news is this is likely a temporary problem. It looks like you have aquasoil in the tank, so your plants just need to develop proper roots in order to tap the nutrients and iron that are in the aquasoil. You won't need to dose iron forever, just a few weeks.
If you don't mind taking more pictures of the iron deficient plants with the digital camera that would be great. I'd love to use these photos in the DeficiencyFinder database so other people in the future can see what iron deficiency looks like in their plants. Do you mind if I add your photos? You will receive full credit for them.