Yes, I put them under a compact fluorescent and as you see in the photo, it is doing much better.
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Thanks for your advice, after flushing / washing the root it looked too puny to be under 400w and didn't want to kill the last feminized seed I had, so it's under a fluo but it will go back under the 400w soon.
Thanks for your suggestions, I'm taking them all into account and as you can see in the photo, the seedling is doing better now. The issue is that being in South America, access to sophisticated supplies, so for instance I don't think I'd find the ingredients if I were to try your soil recipe. Same with something as basic as a pH tester, not easy to find, only found a pH measuring gadget that I can't afford, it was going for a ton of money.
I don't believe it has anything to do with the fluorescent light. So long as they are far away from direct heat from the light, the 400w is absolutely fine, I promise you. I veg from seed under a 600w MH. Just keep the light high if it's hot. You should be measuring temps at the leaf height. So long as it's 80-85 (ime, that's what those size plants want) they would very much enjoy extra light.
A fluorescent will work for the moment, but that seedling has enough leaves on it now that it would benefit from being under stronger light.
Simply going from memory, the main ingredients sere Sunshine soil-less medium with perlite &
mykos, earthworm castings, powdered (Dolomite) lime, Jamaican Bat Guano (be careful with this, it can be hot) blood meal, bone meal, extra
mykos, I'd have to look at the rest. It's nothing too sophisticated. But if you want to grow good plants, you have to give them good food. I grow them out till they are showing 5 leafers, then I transfer to the final pot.
One thing is for sure, the soil mix I'm talking about above (again, that is not complete, but it gives you an idea) runs about $350 here in the States. It isn't cheap.
For ph, I don't personally use meters. I prefer the General Hydroponic chemical tester. It's a little vial, fill halfway with water, add 3-5 drops of solution, shake, compare to colors on bottle. I find a chemical reaction to be more trustworthy than a meter. Cheaper too.
What part of S.A. are you in? I speak/write Portugues, I understand Spanish. Been to Brazil a couple times.
**Edit, I would also be planning to transplant that little girl soon into the final pot, a week or so.