The symptoms of spring sickness.
The plants do fine, flower well, grow properly perhaps last year, perhaps for many years in a row. Then after winter, in the spring they sprout and look fine at first. Later they begin to look sickly, stop growing and die back. Then later all the die-back disappears and the fans resprout and look fine but they are much much smaller than they were last year. Typically they are the size of seedlings and typically there are more fans than there were to begin with in the spring. They recover and no longer show any evidence of having had spring sickness other than their size - they may bloom in the same growing season.
The fans will look nice and green even if they had spring sickness earlier in the year, by now; in fact they will have looked normal but very small quite some time ago. So one cannot usually tell if a plant had spring sickness by looking at it now. One has to watch the plant as it starts to grow in the spring and observe it once a week or more often for many weeks to be able to identify the problem as spring sickness.
I had three clumps of different cultivars with spring sickness this year. All recovered quite some time ago. All have much smaller fans than they did last year. One clump will not flower. One clump has flowered but not nearly as well as last year and the third clump will flower soon. All have had normal green leaves for some time.
The symptoms of growing and flowering well for one or more years in one location and then reducing in size to small fans matches the effect of spring sickness.
