2007 F650GS rear shock/suspension/chain

Hello. I returned home from Cape Town this morning to Riebeek-Kasteel (80km). Bike handled more or less like usual. Then I put the bike on its center stand to lube the chain. Both wheels touched the ground. The chain top part was touching the metal and bottom part sagged a lot. About 12cm play. There was oil/grease all over the rim. I've noticed a gradual build-up of that over the past week or so. What could this be?

The rear shock was replaced three months ago.

There is no technician in RK. Nearest is Cape Town or Stellenbosch. any suggestions? thanks!