Yellow-ish spots in the middle of leaves. What can it be?

See the pic. There are distinct yellowish spots in the middle of the leaves.

This guy is very close to 2 cfl tubes 18w

Using hydro/aero with the pots bottom submerged into water and an airstone under it

It looks like a sun or a nute burn to me

But I'm a total noob, lol

What do you think can it be? I'm using nutes at 1/5 strength since sprouted

So this morning the spots became bigger... strange

I have a lot of bugs crawling on it, mostly flying bugs

Can that affect anything?