Yellowing tops can be caused by too much bloom food too soon. Not the case if you haven't fed it with anything other than what you mentioned.
Another cause can be too much light. How close is your light to the canopy?
Have you changed the distance recently allowing it to be closer?
Others will...
Another issue could be PH if you haven't added dolomite lime or oyster shell flower after a few grows.
Soil PH drops over time and needs to be checked.
If you're going to continue reusing soil a $30 soil test will show if the soil is deficient or at toxic levels and will include a PH test.
I agree with the others that the plant is over fed and has a salt build up.
There is a lot of mis information circulating about soil growing. The salt build up does not happen for growers that buy fresh soil each grow.
Soil does build up salts if reused and never leached of the buildup.
There...
An evaporative cooler holds a couple gallons of water and simply pumps it to the top and gravity runs it through a filter. Air is moved by a fan. RO water and regular cleanings keep it running well.
I have one similar to this...
I was going to suggest the drops.
Rainwater usually tests below 7 ph. It is only in rare locations in the world where rainwater tests above 7.
The drops will give you a more accurate result.
I rarely see a conversation about leaching soil after a few grows. In my experience I find the need to leach every 3 or 4 grows. I went 5 years re amending, about 15 grows with the same soil before sending out a soil sample for testing and it had excessive amounts of sulfur and calcium. Could be...
Lots of good advice.
In the 3rd picture in the 1st post it looks like the green fan is blasting the canopy. The fan should be higher up or directed away from the plant. leaves are not happy when constantly being hit with a fan.