I would suggest thee possibilities, in likely order.

* heating element not fully functional: This could be due to power
supply issues (one half of the 240V supply not functioning resulting
in 120V) or a damaged element, reducing the heat to half, or a high
resistance connection to one or more heater elements.

* Poor venting. Could be lint build up, crimped duct or as noted,
water in the duct at a low point.

* Control problems with the dryer control keeping the temperature as
in delicate cycle.

Good Luck