That temp is low. Guppys do best in the 72-82F range, with 77F being the median...the low temp could be causing the lethargy in the snail, as well...I'd raise the temp
aquariumlabs.com

Guppy Temperature [Ideal Min & Max Guppy Fish Temperatures]
Before you run to the pet store and get your first batch of these beauties, you should learn more about the guppy temperature.
