Chives Coming Up With Flat Leaves

I have planted chives in my garden - we have cut the plant back to the ground and it is not coming up true to form - the leaves are flat instead of round and the flavor is only slight Please let me know what has happened - have they been genetically altered???

I wonder if grass has snuck into your chive patch and since it would rebound faster than the chives after a severe trimming, with only the odd chive leaf providing a chive flavour. Dig out a growth with flat leaves and see if it has a rhizome or a tiny bulb.
The other solution might be that you have garlic chives. They are round when tiny and at maturity the tubular leaves flatten, but still are a tube, just a flattened one. Check the leaves and see if this is the problem. Since onions are happy to hybridize, you could have a plant that took this character from one of its parents -and only the bees know what happened!