Stems Turning To Mush

[Firstman]

I have a problem. I just bought 2 Ludwigia repens from the internet and they arrived Monday w/ other plants ordered. Today ,being Thursday, they have all but completely died . The stems are rotting from the bottom up except for one stem holding on for dear life. The Rotala Marcandra I ordered is doing the same thing except for 2 stems trying to make it. I have a 40 gallon w/ 130 watts 6,700k and 10,000k Sunpaq bulbs. My GH is 3*, KH is 3*, pH 6.8, Ammonia 0, Nitrite 0, Nitrate 0-10 ppm, CO2 about 22 ppm. I use the full line of Seachem Fert products and dose according to their dosing chart supplied on their site. I know that plants will shock when introduced, but the stems don't turn to 'mush'. Any ideas.

 

[aaronnorth]

CO2 seems low for the amount of light you have, try upping it so it is nearer 30ppm

 

[Syphoniera]

Hi, Firstman.
Had the same thing happen - twice; one lot LFS and one from the internet.
In my case, a whole swack of critters, including some kind of voracious, fast-growing plant-eating grub, hatched out of the last lot, from a complete scratch redo of a tank, (L repens set in at at the back, and didn't realize fast enough they'd gone brown and mushy at an amazing rate) and I wound up dumping the lot - substrate and all - and starting over. In 3 (luckily small) tanks.
I hope you wouldn't mind telling me if you found any such problem?

I'd wondered at the time if the sudden, rapid plant death was caused by the nightmare quantity of critters, but gave up on Ludwigia repens in any event.
I knew other low-tech people had grown it without co2 or high lights, and had no such issues pop up...