It could be that moving the hoses during the radiator change out moved the hose on the reservoir and started a leak.
Or worst case, the hoses got pulled hard and the plastic hose connection to the reservoir bottom got cracked or snapped off (the reservoir may be old and brittle.)
I attached this picture below from an online auto parts store, it listed for right at $40.00.
The Medic
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Monday, January 21st, 2019 AT 7:45 PM