Tips of leaves starting to yellow?

Just went down to check on everything and noticed several le af tips have this yellowish color to them. I looked on the chart and there were a few options for tip problems. Any suggestions or should I even worry about this right now?
4x4x6.5’ tent

RDWC system 4 five gallon grow bkts

5 gallon reservoir

1/10 hp water chiller




950 gph air pump

2”x4” air stone in each bucket

12” oscillating fan

1200w king plus led 24” from canopy

6” 400 cfm exhaust fan and filter

Ph level this morning was 6.0 have added ph down

PPM 1255

Water temp 67.6F

Air temp 75.6F

Could that be from heat? I just check on them and decided to measure the height of the light again because they have been growing so fast lately and it was about 15” above canopy I raised it back up now didn’t know if that could of been the cause