Not a problem. But using oxyclean will leave a residue/film behind, and is extremely hard to rinse off well. The trick is to use two buckets, one with oxyclean, the other with a strong (like, way above sanitizer concentration) star san solution. Soak in oxyclean until the labels fall off, quick rinse so you're not carrying over too much oxyclean, into the star san bucket, rinse. The acidity in the star san breaks down the detergent agent that's in oxyclean and gives you a totally clean, residue/film free bottle. You can feel the film from the oxyclean start to break down almost immediately as it goes into the star san.
I have noticed that the star san solution starts to 'break down' and get to be less effective as I put bottles through (this is why I try to get at least some of the oxyclean off before I put it in the star san).
Apparently, vinegar works in place of the star san, but I haven't tried that. I need to get a bottle of vinegar, because I think it's probably cheaper than star san.
On another note, I reuse the oxyclean solution. Probably putting over 100 bottles with labels on them through the same 5 gallon bucket of oxyclean solution 15-20 at a time.
Just to recap, to strip labels off of bottles.
1. Oxyclean soak (overnight at the most)
2. QUICK rinse in the sink
3. Short (like, <1 minute) Star San soak
4. Good rinse, until the bottle feels totally clean and residue free
I would say dump the old solution, from what I've experienced, star san and oxyclean counteract each other.