Minor Discoloration - Please Help

Week 4 of Nirvana Ice grow. I have this under 5 24w flouros. I have plants about 2"-3" from light. Growth has been excellent. Plant is 12-14" tall with lots of growth. I have potted in FFOF and I have added no nutes as of now. FFOF is known to support a plant through veg so I havent added anything. I have used the same source of water since day 1, no issues. The bottom 2 leaves are showing minor signs of discoloration. You can see minor yellow patches starting to appear. Only on the 2 lower leaves, the rest look super. Is this the start of a problem? Should I start adding Nutes now? Please help. Thanks.

whats your ph @ of water looks like a start of lock out i would suggest giving them a light Nitrogen feeding calmag also would do it good

not sure about FFOF but adding some lime also would be a god idea for your soil