It looks like you may have the start of nutrient lock out due to pH issues. Your best bet is to flush out the soil by watering pH balanced water multiple times and get roughly 30-50% run off each time. This will help reset the soil of any build up that may have occurred from the grow thus far.
Proper watering techniques will avoide this. When watering, always water enough to saturate the soil completely and then have roughly 10-20% of run off water. This will prevent any build up in the soil.
Hope this helps.