Having some issues with my first grow

I'm having several issues with my plants which I can't identify with certainty, especially since I'm colorblind and might be missing stuff, so I'll be describing everything as best as I can.

I have 6 plants in a 0.64m² growtent (I know, tiny but I expected at least one or two to die..). 5 super silver haze and 1 northern lights, all autoflowering.

This is the 6th week since putting them in their 11 liters pots in the tent, so it's starting to flower good. I have : -a 400 hps lamp which works for vegetative and flowering states. - An extractor with a carbon filter - a small fan since yesterday

The plants are on a 19-5 schedule at all times light wise. The temperature has been an issue, but unfortunately I couldn't plan for some crazy heatwaves. It got up to 40°C a few times, but generally stays between 20 and 30. I'm trying to keep it at 26 max.

As supplements I use only Biobizz. I have Biogrow, Bioheaven, Rootjuice (not used anymore), Topmax and BioBloom and I follow the chart for rich soil (royal mix).

Watering has also been an issue because of heatwaves. I usually use a little more than half a liter every 2-3 days now, basically until there's quite a lot of runoff in the cups. I'm trying to water a little more now because I was terrified of overwatering but I might be underwatering instead. I'm gonna be honest here, I have to use tap water more and more (resting overnight) and I can't accurately pH test because all I have is small papers that change colours and I can't see those colours at all! My city says it's 7.4 though so that might be an issue. Runoff water is just under 7 however.

The issues I'm having are :

• Yellow leaves eventually falling at the bottom of plants. While this looks like nitrogen deficiency, I have been generous with nutrients (even got a burn early on). My theory is that since I give nutrients in water, underwatering might cause a deficiency.
• clawing top leaves on top of some plants, maybe because if of some wind stress as I figured how to install the fan. Not gone 12 hours later though despite fixing it (light breeze or turned off since)
• a few yellow spots but nothing crazy.
• heat / light burn on the one closest to the lamp but it should be better now
• one of the plants is still kind of in vegetative phase, I made a post about it, but it looks like it's going better.

This is my first grow but I'm really passionnate about the plants. Unfortunately there seems to be so many issues that I am honestly lost. Therefore any advice about what I might be doing wrong is appreciated, regardless of whether it causes the issues I mentionned.

I can provide more pictures if necessary

I know it's a lot to ask to troobleshoot online but I have been up for the better part of the night searching on tons of sites and yet nothing conclusive, so thanks in advance.

 

My pots are 11 liters as of now, so approximatively 3 gallons. I think it's a little late to pot up, especially with autofeminized, isn't it ?