RSS Feed Displays, but gives errors for validators

Feed displays, but does not work properly and I get a lot of complains. When I try to validate it, I get errors:
This feed is valid, but interoperability with the widest range of feed readers could be improved by implementing the following recommendations.
line 49, column 0: description should not contain srcset attribute (8 occurrences)
line 49, column 0: description should not contain sizes attribute (8 occurrences)

Please help me to solve this. My feed url is: https://artbyheart.biz/feed