First Grow

Hello! It can be leaf septoria, that is caused by a fungus or bacteria that attacks the plants in warm wet weather. It stars from the bottom leaves. If the yellow pots star to turn brown definitely is septoria. In this case you must remove the affected leaves. Or it can be a lack of nitrogen, that you need to keep in good high levels in the veg phase, but if there are no leaves falling, maybe that's not the problem cause in this case leaves turn yellow and fall for itself. Nitrogen is what makes leaves green and very important on photosynthesis. Nitrogen leves must be lowered at the begging of flowering stage, to not occur nitrogen toxicity. Be careful with over watering too, let soil dry, give them water for a couple days and they will recover.