Top leaves turning yellow

It could be a led light burn. How far do you keep them away?

Adding FUEL to your pile of information lol.. I think your ph is fine oddly enough without testing, because all your plants are okay right? I see you have 2 others in a diary and those 2 look great.. Have you been feeding this plant the same as the other two?? the ph perfect sensi bloom? If so that could actually be the source of your issues.. Although Iv'e read great things about that product.. You will wanna use the Sensi Bloom during your Bloom phase. Sensi Grow Is what you want to be using. Although it has the nutrients to make your plant grow... Your plant most likely has taken on too much phosphate it needs more nitrogen during this phase.. Check that ph tho ha ha ha lol.

3 different answer.. I ordered ph tester but i have to wait 3-4 days 😓

This is nutrient burn or overfeeding. Easy fix though plant just needs to flushed with ph balance to get rid of the excess salt and nutrients in the soil.

No not underfeeding. simple Ph problem. any feeding with the same water setup will harm it more so no need to water for a while.until you get your ph pen

I just ordered one. Do you think this is under feeding? if so, ill feed her immediatly. Thank you!

Too little it looks like it's drawing from the leaves but you really shouldn't grow blindly my friend so my suggestion is that you should purchase a cheap one.