Problem planting ludwigia and other stemed plants

[epfakan]

So this is my first planted tank and Im almost done with all major problems(snail out break, and a lil bba) but all my ludwigia plants stem all seem to rot away under the gravel. There are new roots growing from the bottom and going up the plant when i leave them float in the tank. I have a 120 gallon w/ 3.6 watts/gal and i use seachem root tab ferts/kent iorn and manganese and just got seachem excel carbon for the bba. I have river rock and eco complete for my substrate. what can I do differently? should i wrap the roots in some thing? thanks

 

[aqua_chem]

What kind of light do you have? Are there fish in the tank? Are these new plants?

 

[epfakan]

I have Power compact 2 96watt pink plant bulbs and 2 65 white 6700K. I have had the plants 3-4wks and have seen some new growth but there are some snails still(im working on it) so other than the snail holes the leaves are growing new lush tips. I have about 80-90 baby severums and thats it raised(dont have the parents any more) and the dont bother the plants at all. The biggest one is less than an inch and most are much smaller.

 

[epfakan]

I cant figure out how to add a pic to the forum? the pic is on my comp but it keeps telling me to insert a link please help