Best coarse of action is to get a fecal float test done. I don't think you can an "at home" testing. Besides, waiting for that to arrive may lose you critical time. If you call around to local vets someone will usually help you out. Last time I did this it cost me $18 to get it done. Great cost for a peice of mind.
If you can't get this done, you can administer both together. I would also use the full dose of corid, not the reduced dose for the second round.
Also, if you are giving a good quality feed, it should have the b vitamins needed for a full rebound after the corid rounds are completed, just don't dilute it with treats, etc while they recover. You can give the vitamins if you feel it is necessary.