If the final segment ctc ctc ttc of the normal hemoglobin dna sequence underwent a point mutation to become ctc ctt ttc, would it affect the resulting protein?

Ascience research group is testing a new type of plant food. one trial is conducted in a controlled experiment. the data from the trial show that the plant that received the new food grew faster than the control plant. the group announces that the new plant food makes plants grow faster. what is the main weakness in this scientific claim?