Gardening Question

Having searched the resources available, yet not having talked to a REAL gardener, I can't find an answer to my question.
Question: after sixteen years, why are the blossoms on these old chrysanthemums so small?
wee mom flowers are on lower right of picture
My stylist this morning said that the roots after all these years probably have worn out.  The Walmart flower seller guy said that genetically, maybe the flowers are just not supposed to bloom after a certain undefined number of years.  So with those expert witnesses to testify on my behalf, the mums will be dug up, discarded, and and replanted with fresh pots of mums.  
Sadly, I must wait at least two weeks until shipments of new mums arrive at the local stores.  Home Depot is my usual supplier.
The red mums above seem to be doing well and are the usual sizes.
Cosmos with flower garland seem happy.
Columbines on second flowering of the season after roots have been shaded with bark and flagstone rock. Some columbines have been moved to different locations, but have not overcome the shock of their rude upheavals, so the pictures would not be pretty if they were shown.  Trust me, those flowers and the daisies that were also dug up and moved are in a sad state of trying to survive in their new surroundings
On a happier note, new hostas have found their places this morning in the wildflower garden, although they really should be banned from living with the wildflowers.  Let's just say the wildflower garden is becoming more civilized with the hostas growing alongside the columbines and penstemon and daisies.
Lots of rain has kept us indoors a bit more the last few days, so I've caught up on Last Tango in Halifax (my new favorite PBS series), Endeavour (another PBS series) and reruns of Midsomer Murders.  John Nettles of Midsomer fame is my new best male friend.  Cannot forget Poirot, either.

Wishing you a big, beautiful bowl of ruby red cherries.  Hope your July ends on a high note!
And if you know why those flowering mums have become so small, please leave me a comment.