Best Light For Fluval 90

[utrin]

Hi Guys i have just started getting into fish keeping, i have a fluval 90 and the standard lights that came with it, some of my plants are looking abit brown and one plant is always rotting at bottom then breaking off. What is the best 2 lights i can buy for this aquarium? i think there T8 fitting..

 

[utrin]

ive been looking everywhere and all i can find is 15 watt light, that come in the 45cm/18inch size, is it impossible to get a 30 watt light thats 45cm?