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2 possible explanations
1/ What brand Plössl eye piece ?
Could be a low cost $30 Plössl which have poor coatings on the optics and poor anti internal reflective paint in the barrel
Could be light scatter ??
Try a more expensive eye piece if using a cheap Plössl, cheap Plössl are notorious for introducing internal optical reflections
2/ Venus is very low at the moment to observe therefore the atmosphere can play havoc depending on your location and geography
Are you observing over ocean ( large waterways ) or land , are you observing from a suburban light polluted environment or rural dark skies ?
Could be atmospheric dispersion or refraction ?
Even expensive good quality eye pieces can be affected when observing at altitudes below 30 deg
Test your eye piece and Barlow combo on a bright Star up nice and high
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