Rootbound and check ph going both in and out.......transplant up into quality soil and it should solve your issues whether they be ph, not enough nutes or rootbound. I will say again....use QUALITY soil.....I personally like Fox Farms Oceans Forest. You may have all three issues.......many symptoms mimic each other and one of the great things about soil growing is that some new fresh QUALITY soil in a new (and hopefully larger) pot will straighten out many problems without you having to know exactly what the issue is.

If you DO want to know exactly what the issue is you would need to make your changes one at a time (check and adjust ph for example) and see how your plants react. That's why transplanting is so great......it really helps with many issues but....again....the key word here is QUALITY soil.

Good luck.