Elocharis parvula stagnating...

Everyone praised this plant as a fast grower and undemanding in terms of light. I was eager to see it spread and form a nice "lawn". However, my (limited) experience is different. I had this plant for like 27 days, so far I didn't see any new growth... Yes few grass blades did grow a bit, but nothing to write home about... with no spreading.

Specs: 250liter aquarium, JBL clay substrate as the first layer, 0,53w/l T5 lighting, CO2 DIY, daily dosage of PPS-pro fertilizers. Before planting, I trimmed it extensively and separated the stems and planted them close to each other.
What to do/try next?

Several weeks, I doubt that's the problem. I also asked this question on another forum and folks said E. parvula needed time to settle in the root.

Thanks Authmal, how often do you change your bulbs?