450 umol max in flowering, how is that possible ? Any idea why I can't have more light ? Thx !

Also give your plants 6 hours darkness, no matter how strong the ruderalis part in them is, a part of them is still a Cannabisplant that needs his 12 hours sleep. If you want big buds you need to let them rest. Also just because ruderalis and so autoflowers can take 24hours never implied that its any close to optimal. I dont know your lightcycles tho, just in case

Fck thats apps, if you put a screenprotector on it doesnt work at all. Also its reflecting certain angles and can only measure direct light from like a 60-140 degree(realistic in a tent is 0-180) intake. The value is always lower, use the measurings of your product or from products with similar watts and specs ( same gen of LEDs etc). Every professional brand provides a PPFD map for their lamps.

is that from a phone app? those numbers are not accurate but they are consistent. if you run into growth patterns that are too tight and visible light damage at what reads as "450", it's probably higher than 450, unless you are running 24/0 cycle maybe. tip burn is not how light damage starts. So, i'd verify your thoughts that the lights are the cause before assuming it. the path to do that is below. You want 800-900PPFD over 12 hours per day - then trial and error adjustment from there. Better to use specs from light, if accurate, than a phone app converting klux. A phone is not a quantum meter no matter what anyone says. Photoperiods on 12/12 .36 m^2 only needs 288-324 umol/s produced by a light. the most efficient possible light on the market could do this with 100w, but less efficient lights you'd need 125-130watts. 18/6 schedule for vege phase or autoflowers 193 - 217 umol/s produced by light. This is simply 67% of the previous values because it is 1:1 inversely proportional to hours of operation. If your light produced more or less than these ranges, then you have to adjust the power knob in a proportional manner. Even if in these rnages, you likely have some fine-tuning to oo, as the variables that amount to "Max DLI" are not the same in every garden, so your max is different from someone else's maximum DLI. Read up on Daily Light Integral. umol/s is a single point measurment. DLI is what matters and allows communication of the idea as apples to apples when you talk about how much light you provide with others. Get the gist of it even if you don't want to learn the math. anyway, if you aren't up around 35-40DLI (based on spec sheet data, not a phone app), it's probably not the light causing what you have seen and more likely nute-related. *900 ppfd is probably too much (assuming 12 hour schedule or 600ppfd on a 18h schedule). This amounts to 38.9DLI. You may need to dial back 5% from there, or not. It's purposely at the high end so that you ahve to back off a bit and be confident you are giving all she can take.

Maybe you need to lower the concentration of feed to account for the brighter light. If the light is brighter and the plant is up taking more fluids it just might need a small tweak to avoid burning. It will also go to say they will need more water over all. so same amount of feed in grams or volume per week, but in a larger volume of water. aka dilution. your plants are looking quite luck so they might be getting to much. Good Luck!