Creeping jenny is spread out about 10 by 10 feet; it usually always flourishes and is bright neon color, soft and thick. This summer it looks dried up with weeds growing in it. I haven't done anything different. I'm in zone 7. Should I fertilize?
Creeping Jenny does need regular watering and mulching can help with moisture retention and weed control.
I would not fertilize now, wait until spring.
Here is a link with more growing information.