Overwatering, Underwatering or heat stress?

Hi guys, these plants sprouted on the 10th of July and after a few days they started to give problems... usually I never use such big pots since I prefer to let them stabilize first in very small pots and then transplant in the final pot but this time I had these pots under hand and I continued with them. The plants probably suffered initially from too much water but I tried to let the soil dry out thoroughly and then start giving water normally again but there still seems to be some problem! I don't understand if it is still resulting from too much water, too little water or if it is because the soil has become hydrophobic. What do you recommend me to do? At the moment there is neither one that is the most fragile one that has slowed down instead the others seem to be proceeding after the problem.
I must admit that it is so hot (outside 44° Celsius and inside the box maximum 29° Celsius) I was thinking that the problem might have been first the water and now the heat if not both. What do you recommend me to do?

David August said:

too little water or if it is because the soil has become hydrophobic

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I do believe that's it, now you know when it's too dry, don't let it get that dry again.
If they're still dry/light, sit them in a couple of inches of water.
The damaged leaves aren't going to get better, so look at new growth to gauge what's happening.

Good luck

Hugo Phurst said:

I do believe that's it, now you know when it's too dry, don't let it get that dry again.
If they're still dry/light, sit them in a couple of inches of water.
The damaged leaves aren't going to get better, so look at new growth to gauge what's happening.

Good luck

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For the hydrophobic soil I wanted to try a drop of soap, which is supposed to be surfactant! anyway it was probably because I left the plants 4 days without water because the pots were still heavy, but now as soon as I have given them water again (practically dividing almost a litre of water and if you see the middle one on the right it has behaved again as if I had given it too much water! I gave the water on the 22nd.

Now I wanted to try to lower the temperature anyway since I am afraid that it will dry out the first layer of soil too much, become hydrophobic and then become difficult to get water to penetrate below.. the damage to the leaves of showed up when they froze for a few days with the new growth tending to yellow but they seem to be growing again but those damaged leaves at the bottom continue to dry out and it gives me the idea that it is a problem that still persists.. do I water tonight? Or do I leave it until tomorrow? Those are my doubts
thank you very much for your good advice