Leaves light Green? Some kind of deficiency? Ready for transplant?

my substrate is composed of 90% peat + perlite and 10% humus (maybe the sub Just ran out of nutes, since I mixed only 10% organic?). Oh, runoff ph is 6,3-6,5. Another thing I noticed was that the older/lower leaves are darker in color, but new growth tends to have that more yellowish color. Should I start nutes 1/4 Max strength? Should I Just transplant? Should I do both? And temperature is a little high (90⁰F/30⁰C). But now I am openning the grow door, trying to lower the temp. Could the lighter color Just be from the high temp?