I'm not sure what the effects of fertilizer balls are - it's never happened to me. But I have seen many people warning against them, so you should probably keep a very close eye on the progress of your cham.
However, what I did want to mention is that you might want to think about putting up a mesh screen over your pots to prevent the cham from getting at the soil, and swallowing things like stones/fertilizer.
I use a plastic mesh (just under 1/4inch screen) that garden centres sell as a backing/support for climbing plants. I simply cut it with scissors to match the shape of the pot, and cut a hole to the centre so I can get it around the trunk of the plant, then use cable ties to keep it down.