Lung VQ Scan. Also known as lung or pulmonary ventilation (V) and perfusion (Q) scans. A lung VQ scan is an imaging test that uses a ventilation (V) scan to measure air flow in your lungs and a perfusion (Q) scan to see where blood flows in your lungs. It uses special x ray scanners outside of your body to create pictures of air and blood flow patterns in your lungs.
Yellow leaf spot, also known as leaf septoria, are caused by Septoria cannabis and S. neocannabina. These are fungal pathogens aimed specifically at marijuana plants. It is brought about by warm weather and rain and effect marijuana grown outdoors.
If your dryness problem is just affecting the oldest leaves that don't get much light anymore, you shouldn't worry. If the leaves affected are the ones which are closest to your lights, it's possible that the crispiness is a result of 'light burn' or 'heat burn'. You can tell if this is the cause because the only cannabis leaves affected are the ones closest to the lights or source of heat. If the dryness affecting leaves that are new growth, it's possible that you are you are giving your cannabis too many nutrients and it's showing the first signs of nutrient burn.