Hey there, i would cut any leaf that's more than 70% damaged, but i wouldnt cut all the leaves just so you can see if the problem is spreading or not. First i just want to say, dont worry so much about the breeder timeframe, many times, it's just not true, most of the time you need a few weeks more, and anyway you dont know what conditions the plant should be in to get that kind of schedule. So it's not your fault and you shouldnt worry ! Second i see some problems there, i see so N deficiency - this you can recognise from the yellowing and dying of the leaves lower on the plant. Second I see the start of a magnesium deficiency, this you can see from the yellowing of other leaves starting from between the veins and the sides of the leaves. Easy to fix : cut out the kelp and double the flower power and the cal mag. To answer your final question about the growth rate : growth rate is controlled by the plant's metabolism which is regulated by the VPD (vapor pressure deficit) this is a formula about the humidity and the temperature. So i see you have high temperature and humidity, and this basically makes the plant grow a bit slower than normal, so that's why you have some problems. Also your pH... it's just a little bit high, should be 6 - 6.5 (if you cut the kelp then it will help lower the pH) ... all these things add up over time... Anyway, hope this helps ! š