I coyldnt find a 6500k bulb at my Home Depot, but I went to a hardware store across the street and they had 15 and 20 watt bulbs. They were the GE brand... Only $7 for the 15 watt. Not only is the light important, but way more important is the reflector quality, LEDs are different with this, a Zoo Med T5 reflector is Crap compared to a Tek fixture. With the same bulbs you can have low-medium light with the zoo med fixture at a given height and the Tek fixture can give out high light at an even higher height. So reflectors on normal lights are super important.
Dwarf hairgrass is a intermediate plant, it needs good fertile substrate, CO2, and medium-high light. Just having a powerful bulb doesn't mean anything, you don't have the proper Kelvin rating and way too high wattage of a bulb. In my 5.5 gallon tank I am trying my hand at hairgrass and was advised to have my 15 watt light at 24 inches above the substrate for medium light.
15 Gallon NPT
1g no tech bowl in the making