I wonder if it could be The Mind Pool by Charles Sheffield, published 1993.
The flower was engineered by a scientist called The Margrave aka Fujitsu:
The Margrave stared at them gloomily and nodded. He closed the door and triple-locked it, then turned and pressed a light switch. At the other side of the room sat a bulbous plant, five feet high and about two feet across. When the light went on the leaves of the swollen upper part began to open. In less than thirty seconds a single vast flower was
revealed. Its central part resembled a human face, with pink cheeks, curved red mouth, and blind blue eyes. After a few moments, the mouth opened. A thin, beautiful tone came forth, a crystalline, pure soprano singing a wordless lament. The song continued and broadened, from a simple theme through to a complex coloratura embroidery.
The instellar probes are called Morgan Constructs. They were designed to explore the universe, but something went wrong and they turned out to be hostile to all life forms. There were seventeen of them originally but fourteen were destroyed in their escape attempt leaving the three you mention, though two were subsequently killed. The rest of the book is about the hunt for the last construct.