Crispy leaves

Definitely a nutrient and/or pH issues. Start a diary so we can help you better. So many parameters as to what could be involved but basically no info to find clues to the answers.

looks like the edges of your leaves are beginning to curl up too. this is a classic sign of heat stress :) the yellowing can be lack of nitrogen if its starting at the bottom of the plant and working its way up it could also be a slight imbalance in your ph so ,be sure to check your feeding parameters and ph level. most growers will advise you only use half of recommended dosage of nutrients though I don't follow this practice I use the feed table that comes with my nutrients as the dosages have already been worked out for you for optimal plant health we would all be wise to follow them my opinion :)