I suspect your baking pans are tin and the rust is oxidisation caused by exposure to the air while still wet. Try getting the rust off with a brillo pad, then wash well and dry them thoroughly. I dont think the rust will harm you anyway. I went camping years ago and we had one steel paella pan for everything and we had rust with everything we ate for two weeks, sort of a condiment that came free of charge. You can wipe them with oil to prevent rust coming back but getting them dry is the key.