Well as of yesterday I would have said yes, that is too low. But then I came upon this post on repticzone.com...

"First, lets just nip a major misconception in the bud. Ball pythons do not dig heat. I know it’s hot in Africa. However there are ways to avoid heat pretty much anywhere where it is hot and ball pythons do just that. So these 90+ degree basking spots that most care sheets you will find are nothing more than regurgitated widespread misinformation. In the wild, they are mostly nocturnal during the hot summer months, spending their days in cool, humid burrows. Many of them are found on the breezy coastal plains where all they have to do is find a shady spot to stay cool. They do most of their moving around and hunting in the cool of the night. It doesn’t hurt to have a 90 degree basking spot as long as you have room for a highly varied gradient so they can escape it and enjoy temps that they actually prefer 70s and 80s. The more gradient you have, the happier and healthier your ball python will be."

If you still want to bump up temps you could always slap another UTH on.