Mileage has dropped from 51mph to 33mph!! on 2012 Honda Insight

Recently I had a problem where ABS, Brake System and VSA lights turned on but after check at dealership found out that due to low battery bcoz of no use for a month car had electronic system failure so they reset the system but since then mileage of my car has dropped significantly from being 51 to around 33 also I am feeling sluggishness in the pickup. Any advice guys what could be causing this problem car has 8500 miles on it and I drive around 10miles a day only

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2 answers 2 comments
should be under factory warranty, return and ask questions
sure will do, Thanks!!
Is the IMA system working properly , including 'auto-stop' Is yours manual or automatic trans?
Yes IMA is working and auto stop is also working it is automatic transmission