Question
I HAVE BLACK EYED SUSANS PLANTED IN THE GROUND NEAR MY MAILBOX. THEY DID WELL THE FIRST YEAR. EVER SINCE THEY FLOWER VERY LATE (last week) AND SCANTILY.  The petals are narrow and pathetic. THEY ARE PLANTED IN PART SUN -- AFTERNOON SUN I BELIEVE.   EVERYONE ELSE IN THE NEIGHBORHOOD'S FLOWERS A LOT EARLIER WITH TONS OF FLOWERS.  I SPRAYED THEM WITH ANTI BUG THIS YEAR, WATERED THEM...  STILL NOT GOOD.  EVEN THE FEW OPEN FLOWERS ARE WEAK LOOKING.  I LIVE IN CT.  THANK YOU!

Answer
Linda,
If a plant looks weak, it isn't insects.  The most common reason plants look weak or feeble is something at root level - in the ground, and usually NOT disease.  I'll go over a few possibilities here, and you can decide which fits best:
If your plant is growing in a very dry area, the plants and flowers will be smaller.  Although these plants are drought tolerant, a deep soaking once a week, and a yearly application of compost or composted manure over the surface of the soil around the plant, will make the plants larger and more robust.

If the soil is low in fertility, the plants will be smaller.  One application of fertilizer is plenty for black eyed susans, in addition to the compost mentioned above.  Fertilize in May.

Do you have clay soil?  Just as too dry can cause weak plants, too wet will do the same.  Not much you can do about a wet year, but if they are in a low spot that is prone to moisture, you'd be better off planting something else there.

Do you know what type of black eyed susans you have?  Goldstrum Rudbeckia is the one that flowers late summer - late July into August.  Could it be that you are comparing yours  to another type of Rudbeckia you see around the neighborhood?  Are you sure that the other ones you see are the same plant?  

Rudbeckia hirta has larger flowers and comes into bloom earlier in the season.  It is still in bloom now.  This rudbeckia, sometimes called Gloriosa daisy, is actually a biennial - it grows one year, blooms the next and then dies, but usually self seeds.  The flowers are twice as big as the other types of rudbeckia.

If you are seeing the same Rudbeckia, I would suspect that the growing conditions are the problem (moisture and fertility)

I hope this helps!
C.L.