If so why, because I just did now I'm wondering...
The biggest problem is when the mix contains fertilizers. If the ingredients are literally nothing but peat, perlite, and vermiculite, then you're probably good, but a mix like that can be very hard to find, so you have to be careful. Miracle-Gro is probably the most common brand of gardening supplies, and they pretty much always add extra fertilizers to their stuff.
Perlite and vermiculite do not affect nutrition or pH in any way. They are just here to aerate the roots, and helps them absorb nutrients better. So it shouldn't be a problem at all.
