Runtz muffin Barney’s farm

It looks to be micro nutrients deficiency ( cal mg ) at first glance. This could be causes by a few different things. Not enough micro nutrients for which you would add these nutrients. Ph problems for which you should test run off and or soil. If ph is off correct ph by changing ph of water and monitoring. Sometimes too much of one nutrient will lock out other nutes. So check for signs of over feeding with any nute. ( nit toxicity ect ). If so flush with ph water then add nutes back ( with cal mg as you probably washed put alot of micro nutes ) at a weaker solution. Another thing to check could be lights light burn or od. Too much light can look similar to cal mg deficiency but it's from too much light in some areas ( will be only at top plant and focused on tips. Good luck and your grow is looking good.