It could be, but at the moment, as you said, they look good. A pH value of 5.8 to 6.5 is good, with plants in the flowering stage increasingly preferring a higher pH value, around 6.4 to 6.5. It's also normal for your drain to have more PPM than what you pour in from above, as they collect the salts that the plants do not absorb. Just water them occasionally with plain water without nutrients and adjust the pH value. But as I said, they look very healthy.