Well, I have been problems with my jungle vals and I am finally having them do well- after 8 months of melting, death an decay. There were many problems in my tank to contribute to this:
> I used excel. If you want to use excel with vals, you must use only small doses and add it to the tank gradually, not all in one big dump. Even this will likely melt them.
> I had regular gravel. When I had inert aquarium gravel my vals hated their life and just died off over eight months. They need a nutrient rich substrate like Flourite or Ecocomplete as they are very heavy root feeders.
> I didn't dose enough or the right stuff in ways of fertilizers. They need a lot of macronutrients, like nitrogen, phosphorous and potassium. If you are not dosing these they might have trouble.
> I had low light to start them with, and until I added good plant lights did they start to enjoy life again.
I bought mine last October (as you can see if you check out my journal) and it wasn't until I think roughly a month ago did they just continuously melt and die off. I started with a tonne of the stuff and ended up with a very small amount left. Once I added more light to my tank, put them in flourite, dosed a liberal amount of N and trace (Flourish) did they start to grow again. They sent out a few runners when I did this. Then I stopped dosing excel and started a DIY CO2 reactor. They sent out a lot of runners at this point- I more than doubled the number of plants in a month. Once I started dosing K and P they really started to grow vertically as well and produce more leaves.
Moral of the story? Dose macronutrients N, P, and K, give them a nutrient rich substrate, good lighting, and real CO2 (not excel) and let them adjust to the tank as they tend to die off initially in anyone's tank.