The "blend" cypress mulch at Lowes and Home Depot is only 10% cypress, I called the manufacturer and asked. Otherwise it's 50% pine and 40% "whatever we were cutting that week", which could include black walnut or even cedar. They absolutely did not recommend it as reptile substrate.
Ohhh well in that case i wont be buying any of that stuff
High humidity is just fine temporarily. I would bet your BP might appreciate the bump up for a small reprieve. As long as there isn't standing water and the BP isn't soaked then you're all good. Even with minimal ventilation the humidity will level out over time. I guarantee that some other forum members will tell you otherwise, but IMO and the opinion of rational herp keepers out there, there's nothing to worry about.
You can always do a mix. Use a dryer substrate like retibark and mix it with the cypress mulch.
I use cypress for my boa and it will dry, pretty quickly too. It usually only stays on the higher end for a day or two and it will start to dry up. Ball pythons are fine to have a few days of higher humidity, it wont hurt your snake. You will find yourself spraying the cypress in about a week or two.
Yes, good points! I agree. You can even use a smaller amount of cypress mulch as well. Good thing your enclosure is well ventilated that will make it more tolerable for the reptiles. Also the fact that you are not keeping them at high humidity extremes for a long periods of time. Imo, cypress mulch is one of the better substrates out there but only the 100% cypress mulch. Good luck.