What are the dimensions of the tubs?

53% is okay. Personally, I like to keep it a bit higher, around 60%, and during sheds, it's helpful to have it around 70%.

81* as an ambient temperature is great, but BPs like a basking spot (warm area under a hide) of around 90-95*, although all snakes are different. If my girl's warm spot gets any higher than 93*, she moves to her cool hide.