Help! Why are my leaves turning yellow?

Daily Light Integral The daily light integral (DLI) you provide is 58.3 mol/m²/d whereas the ideal is 34 mol/m²/d. Calculated from your light figures,I'd say your problems light too bright/near,stressing it out. ( your excellent details provided make me very confident this is your problem,well done) You may find this useful! https://growlightmeter.com/calculator/ Be lucky! Less warp engine! OK, had a better look and yeah,too close to light! I have that light in my collection,I use it for veg stage in a 4x4, know it well. Only good for 3 x 3 flowering and has a very uneven PAR footprint concentrated central. 🚨 RED ALERT! The plant looks generally good,problem is tops getting too much heat/light stress. Hopefully you can raise the light? If not you are going to have to get creative on how to provide the correct light requirements for the situation,even use of the dimmer won't help that close. Been through your pain of growing. You are on the right path!