They can't stay pretty forever, those spots may be nute burn, just chill on the fert for the rest of its life (since you have 2-3 weeks left), give fresh water. your plants may need another 3 weeks to really fatten up, you say you're on day 40, right? I'd go at least to day 60. They look good for 2 40w CFLs by the way, good job!