HEY JACOB...

that water ph tester is perfect... every grower has a few of those laying around his house.. that should become your best friend...

You plants do look very good..obviously there is a problem but your growth and leaf size are GREAT...

I would stop giving them nutrients for a couple waterings...

Can you transplant them?
How big are those pots?
Can you transplant them into the next biggest size container?
Is the new growth still GOOD.. and better than previous growth? Each new set of FAN leaves should be more impressive than the previous set... this is a sign of a healthy plant...

iloveyou