Plants keep dying...thinking its a light issue?

[Friendlyfishies]

My plants keep melting and turning brown. I feed sechem flourish liquid and root tabs but no luck. My plants did awesome, grew wonderfully and bright green in my 10g with 6500k plant lights...I moved them to my 20g long with the a 6500k light but it didnt look as bright as my 10 gal, thats why im thinking perhaps its a light issue.

Should I upgrade my bulb or go low-tech...
If I go low-tech I need some good ideas for really hardy low tech plants
If I upgrade my bulb (if you think thats the problem) what k rating should I try this time?

[aokashi]

which plants are these?
can you also give the stocking, temperature lighting and whatever else you think may be releavant about the two tanks?

[Friendlyfishies]

20 gallon long
1 male betta
3 nerite snails (2 of which will soon be moving)
10-20 gallon rated filter
black sand
sechem flourish tabs in sand
Sechem flourish liquid ferts
lights on 12 hours daily (auto timer)
78 degrees

Had some hair algea but I increased vacs and it went away.

I had
crypt (partially died)
Wysteria (roots melted)
Chain Sword (leaves melted incl roots)
Hornwort (needles melted, stopped gowing)

All of these plant were doing awesome in the 10 gal with 2 6500k lights, growing like mad!
Same ferts being used
Now in the 20 gal long tank with a single tube 6500k bulb, nothing is surviving. My last plant left, little swords are doing alright though right now, not sure if they will last or not?

Ph is high 8.0-8.2 but its always been that, betta does fine with it and plants didnt seem to mind it when they were in the 10 gallon.
all other readings are 0, its uncycled and I do water changes et.

[aokashi]

you will need to give the 20 gallon another light or two it seems..
most plants prefer high PH and harder water, so that is fine. in a 20 gallon, just a betta and three snails is almost no bioload to help the plants.

put in the lights first and see how it goes, some plants may simply be adjusting... did you get these plants new or were they from your ten gallon?

[Friendlyfishies]

I got them in the fall and they did awesome in the 10 gal, all plants transplanted from the 10 gal to the 20 gal except the wysteria, that was the only new plant that I added, everything else was already adjusted to our water and doing great til I moved them :(