Ya phoenix worms are a good source of extra Calcium. Also for your crickets have them eat some fresh cut potato and dark leaf greens (make sure they're organic). Those boast decent amounts of calcium, which will be absorbed by the crickets. Also earthworms have an excellent Phosphorus to Calcium ratio, which will greatly aid in bone growth and density - plus earthworms are cheap, easy to keep, and find (whether outside or at a store).