Baby Leaves Turning Yellow

my plants are about 4 weeks old and about 9 inches tall
i water them about every three days and when i planted them i put in about a teaspoon of manure pellets into the pot
other than the baby leaves turning yellow the plants look very healthy
anyone know what i can do to solve this problem?

o yea i am growing them outside where the temperature is mid eighties for the high and 60 for the low

New leaves comin out are yellow?

no everything is lloking very healthy except for the baby leaves which are wilting and yellow

this has also hapned to me from time to time and i have nothing to atribute this phenomana to