I just found this snippet on the net:

[]Is it just an old wife's tale that Vallisneria and Saggitaria or
Cryptocoryne and Vals(?) do not thrive when kept in the same tank? I just
set up a 20 gallon with Vallisneria tortifolia and Saggitaria subulata at
opposite ends.[]

Now, when I first started my tank I had lots of spiral vallis and it did
fine, especially in the hard water here. But I added some plants and 3
crypts and the Vallis died eventually. I wondered, as I know it normally
grows like weeds, but didn't think too much about it.

I then set up to small tanks. They haven't got much light, so I planted them
mainly with Crypts, but they both get direct light from a window on one side
and I planted Vallis on that side to provide some shading. Again the Vallis
died, this time even quicker.

Has anyone got any experience of Vallis (especially the small ones) and
crypts in tanks ?

Greetings
Mad