I put in a large mangrove last night. I have been running my pH at 6,6 with a KH at 4. This morning when I checked pH it was 6,4 (usually it is 7,1 before the Co2 kick's in) and the KH had dropped to 3. The water was a little bit brown.

I just cleaned the mangrove with running water before i dumped it in the tank. It had some leftovers of javamoss on it, so I figure it has been in a tank before.

The pH/KH chart doesnt mach anymore (the Co2 wont kick in as it is set on ph 6,6 so it cant be 35ppm of Co2 as the chart says)

What causes this and what should I do to get back on track again...?

Vidar