My Kumquats are the hungriest out of all the citrus I have, and I have a lot.
I just about have to spoonfeed the kumquats potassium and nitrogen, and lots of foliars. There are foliars I alternate weekly and they love it and respond within days to each feeding with flushes of growth, flowers, fruit, etc.
You fertilized last year and growing in 100% cow manure. Your tree is very hungry, stressed, and you might have some root damage.
I'm finicky about what I grow my citrus in and make my own soils out of a concise combination of mixed particulates. You must get her on a steady feeding and I suggest a different soil medium for starters.