Rock and a hard place!

Fertilizers maybe. Can you explain more about your setup and lighting?

Fertz for sure. I use heathers in all my tanks and keep a constant 74F temp. For a 10g a 50w or 75w heater should do the job. I use a 50w for my 10g and it does the job.

For cheap, I'd go with mineralized topsoil or plane topsoil under your substrate and 2-t8 bulbs or 2 spiral CF bulbs for light.

DHG doesn't demand much. I neglected it in a 2.5 gallon tank with just ADA Amazonian II subtrate and 9 watt plc tube bulb grew like crazy. Neglected meaning, I don't tend to it, it had no live stock of any sort so at times the light was on for days and at time light was off for days. It still grew and spread out. Didn't grow too tall 2'' - 2.5''. Still healthy green no sign of any coloration. I believed the ADA substrate gave it plenty of nutrients in it's root system. No dosing was done. No heater, no filter. Will I grow it again, nope, not my type of foreground plant. A little too messy when trimming and its root system is just crazy.

I'd replace those incandescent bulbs. Otherwise it's not very demanding. CO2 and ferts always help of course.